ANNEX 2 ALBERT R. MANN LIBRARY New York State Colleges OF Agriculture and Home Economics Cornell Universit\' Cornell University Library TX 551.S7 Human foods and their nutritive value, 3 1924 000 936 819 Cornell University jbrary The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31 92400093681 9 HUMAN FOODS AND THEIR NUTRITIVE VALUE THE MACMILLAN COMPANY NEW YORK ■ BOSTON • CHICAGO ATLANTA SAN FRANCISCO MACMILLAN & CO,, Limited LONDON • BOMBAY - CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA, Ltd. TORONTO HUMAN FOODS AND THEIR NUTRITIVE VALUE BY HARRY SNYDER, B.S. PROFESSOR OF AGRICULTURAL CHEMISTRY, UNIVERSITY OF MINNESOTA, AND CHEMIST OF THE MINNESOTA EXPERIMENT STATION Heto g0rk THE MACMILLAN COMPANY 1908 Ail rights rf served Copyright, 1908, Bv THE MACMILLAN COMPANY. Set up and electrotyped. Published November, 1908. J. S. Gushing Co. — Berwick & Smitli Co, Norwood, Ma^.s., U.S.A. PREFACE Since 1897 instruction has been given at the Uni- versity of Minnesota, College of Agriculture, on human foods and their nutritive value. With the development of the work, need has been felt for a text-book present- ing in concise form the composition and physical prop- erties of foods, and discussing some of the main factors which affect their nutritive value. To meet the need, this book has been prepared, primarily for the author's classroom. It aims to present some of the principles of human nutrition along with a study of the more com- mon articles of food. It is believed that a better under- standing of the subject of nutrition will suggest ways in which foods may be selected and utilized more intel- ligently, resulting not only in pecuniary saving, but also in greater efficiency of physical and mental effort. Prominence is given in this work to those foods, as flour, bread, cereals, vegetables, meats, milk, dairy products, and fruits, that are most extensively used in the dietary, and to some of the physical, chemical, and bacteriological changes affecting digestibility and nutri- tive value which take place during their preparation for the table. Dietary studies, comparative cost and value of foods, rational feeding of men, and experiments VI PREFACE and laboratory practice form features of the work. Some closely related topics, largely of a sanitary nature, as the effect upon food of household sanitation and storage, are also briefly discussed. References are given in case more extended information is desired on some of the subjects treated. While this book was prepared mainly for students who have taken a course in general chemistry, it has been the intention to present the topics in such a way as to be understood by the layman also. This work completes a series of text-books under- taken by the author over ten years ago, dealing with agricultural and industrial subjects: "Chemistry of Plant and Animal Life," "Dairy Chemistry," "Soils and Fertilizers," and " Human Foods and their Nutritive Value." It has been the aim in preparing these books to avoid as far as possible repetition, but at the same time to make each work sufficiently complete to permit its use as a text independent of the series. One of the greatest uses that science can serve is in its application to the household and the everydav affairs of life. Too little attention is generally bestowed upon the study of foods in schools and colleges, and the author sincerely hopes the time will soon come when more prominence will be given to this subject, which is the oldest, most important, most neglected, and least understood of any that have a direct bearing upon the welfare of man. HARRY SNYDER. CONTENTS CHAPTER I PAGE General Composition of Foods i Water ; Dry Matter ; Variations in Weiglit of Foods ; Ash ; Function of Ash in Plant Life ; Organic Matter ; Products of Combustion of Organic Matter ; Classification of Organic Compounds ; Non-nitrogenous Compounds ; Carbohydrates ; Cellulose ; Amount of Cellulose in Foods ; Crude Fiber ; Starch ; Microscopic Structure of Starch ; Dextrin ; Food Value of Starch ; Sugar ; Pectose Sub- stances ; Nitrogen-free-extract ; Fats ; Fuel Value of Fats ; Iodine Number of Fats ; Glycerol Content of Fats ; Ether Extract and Crude Fat ; Organic Acids ; Dietetic Value of Organic Acids ; Essential Oils ; Mixed Compounds ; Nutritive Value of Non-nitrogenous Compounds ; Nitrog- enous Compounds ; General Composition ; Protein ; Sub- divisions of Proteins ; Crude Protein ; Food Value of Protein ; Albuminoids ; Amids and Amines ; Alkaloids ; General Relationship of the Nitrogenous Compounds. CHAPTER n Changes in Composition of Foods during Cooking and Preparation . . 27 Raw and Cooked Foods compared as to Composition ; Chemical Changes during Cooking; General Changes affecting Cellulose, Starch, Sugar, Pectin Bodies, Fats, VUl CONTENTS PAGE Proteids ; Effect of Chemical Changes on Digestibility ; Physical Changes during Cooking ; Action of Heat on Animal and Plant Tissues ; Amount of Heat required for Cooking ; Bacteriological Changes ; Insoluble Ferments ; Soluble Ferments ; Bacterial Action Necessary in Prepa- ration of Some Foods ; Injurious Bacterial Action ; Gen- eral Relationship of Chemical, Physical, and Bacteriological Changes ; Esthetic Value of Foods ; Color of Foods, Natural and Artificial Colors ; Conditions under which Use of Chemicals in Preparation of Foods is Justifiable. CHAPTER III Vegetable Foods 37 General Composition ; Potatoes ; Chemical and Me- chanical Composition ; Uses of Potatoes in Dietary ; Sweet Potatoes ; Carrots ; Parsnips, Cabbage ; Cauliflower ; Beets; Cucumbers; Lettuce; Onions; Spinach; Aspara- gus ; Melons ; Tomatoes ; Sweet Corn ; Eggplant ; Squash ; Celery ; Dietetic Value of Vegetables ; Nutrient Content of Vegetables ; Sanitary Condition of Vegetables ; Miscellaneous Compounds in Vegetables ; Canned Vege- tables ; Edible Portion and Refuse of Vegetables. CHAPTER IV Fruits, Flavors, and Extracts . . .48 General Composition ; Food Value ; Apples ; Oranges ; Lemons; Grape Fruit; Strawberries; Grapes; Peaches; Plums ; Olives ; Figs ; Dried Fruits ; Uses of Fruit in the Dietary ; Canning and Preservation of Fruits ; Adul- terated Canned Fruits ; Fruit Flavors and Extracts ; Syn- thetic Preparation of Flavors. CONTENTS IX CHAPTER V PAGE Sugars, Molasses, Syrup, Honey, and Confections . 58 Composition of Sugars ; Beet Sugar ; Cane Sugar ; Manufacture of Sugar ; Sulpliur Dioxid and Indigo, Uses of, in Sugar Manufacture; Commercial Grades of Sugar; Sugar in tlie Dietary ; Maple Sugar ; Adulteration of Sugar; Dextrose Sugars ; Inversion of Sugars ; Molasses; Syrups ; Adulteration of Molasses ; Sorghum Syrup ; Maple Syrup ; Analysis of Sugar ; Adulteration of Syrups ; Honey ; Confections ; Coloring Matter in Candies ; Coal Tar Dyes ; Saccharine. CHAPTER VI Legumes and Nuts yi General Composition of Legumes ; Beans ; Digesti- bility of Beans ; Use of Beans in the Dietary ; String Beans ; Peas ; Canned Peas ; Peanuts ; General Compo- sition of Nuts ; Chestnuts ; The Hickory Nut ; Almonds ; Pistachio ; Cocoanuts ; Uses of Nuts in the Dietary. CHAPTER VII Milk and Dairy Products 80 Importance in the Dietary ; General Composition ; Di- gestibility ; Sanitary Condition of Milk ; Certified Milk ; Pasteurized Milk ; Tyrotoxicon ; Color of Milk ; Souring of Milk ; Use of Preservatives in Milk ; Condensed Milk ; Skim Milk ; Cream ; Buttermilk ; Goat's Milk ; Koumiss ; Prepared Milks; Human Milk; Adulteration of Milk; Composition of Butter; Digestibility of Butter; Adul- teration of Butter; General Composition of Cheese; Digestibility ; Use in the Dietary ; Cottage Cheese ; Differ- X CONTENTS ent Kinds of Cheese ; Adulteration of Clieese ; Dairy Products in the Dietary. CHAPTER VIII Meats and Animal Food Products . General Composition ; Mineral Matter ; Fat ; Protein ; Non-nitrogenous Compounds ; Why Meats vary in Com- position ; Amides ; Albuminoids ; Taste and Flavor of Meats ; Alkaloidal Bodies in Meats ; Ripening of Meats in Cold Storage ; Beef ; Veal ; Mutton ; Porlc ; Lard ; Texture and Toughness of Meat ; Influence of Cooking upon the Composition of Meats ; Beef Extracts ; Miscel- laneous Meat Products ; Pickled Meats ; Saltpeter in Meats ; Smoked Meats ; Poultry ; Fish ; Oysters, Fatten- ing of ; Shell Fish ; Eggs, General Composition ; Digesti- bility of Eggs ; Use of Eggs in the Dietary ; Canned Meats, General Composition. CHAPTER IX Cereals Preparation and Cost of Cereals ; Various Grains used in making Cereal Products; Cleanliness of; Corn Preim- rations ; Corn Flour ; Use of Corn in Dietary ; Corn Bread ; Oat Preparations ; Cooking of Oatmeal ; Wheat Prepara- tions ; Flour Middlings ; Breakfast Foods ; Digestibility of Wheat Preparations ; Barley Preparations ; Rice Prepa- rations ; Predigested Foods ; The Value of Cereals in the Dietary ; Phosphate Content of Cereals ; Phosphorus Re- quirements of a Ration ; Mechanical Action of Cereals upon Digestion ; Cost and Nutritive Value of Cereals. CONTENTS XI CHAPTER X PAGE Wheat Flour 133 Use for Bread Making; Winter and Spring Wheat Flours ; Composition of Wheat and Flour ; Roller Process of Flour Milling ; Grades of Flour ; Types of Flour ; Com- position of Flour ; Graham and Entire Wheat Flours ; Composition of Wheat Offals ; Aging and Curing of Flour ; Macaroni Flour ; Color ; Granulation ; Capacity of Flour to absorb Water ; Physical Properties of Gluten ; Gluten as a Factor in Bread Making ; Unsoundness ; Comparative Baking Tests ; Bleaching ; Adulteration of Flour ; Nutri- tive Value of Flour. CHAPTER XI Bread and Bread Making 158 Leavened and Unleavened Bread ; Changes during Bread Making ; Loss of Dry Matter during Bread Making ; Action of Yeast ; Compressed Yeast ; Dry Yeast ; Pro- duction of Carbon Dioxid Gas and Alcohol ; Production of Soluble Carbohydrates ; Production of Acids in Bread Making; Volatile Compounds produced during Bread Making; Behavior of Wheat Proteids in Bread Making; Production of Volatile Nitrogenous Compounds ; Oxida- tion of Fat; Influence of the Addition of Wheat Starch and Gluten to Flour; Composition of Bread; Use of Skim Milk and Lard in Bread Making; Influence of Warm and Cold Flours in Bread Making; Variations in the Process of Bread Making; Digestibility of Bread; Use of Graham and Entire Wheat in the Dietary ; Min- eral Content of White Bread ; Comparative Digestibility of New and Old Bread ; Different Kinds of Bread ; Toast. Xll CONTENTS CHAPTER XII PAGE Baking Powders i86 General Composition ; Cream of Tartar Powders ; Resi- due from Cream of Tartar Baldng Powders ; Tartaric Acid Powders ; Phosphate Baking Powders ; Mineral and Organic Phosphates ; Phosphate Residue ; Alum Baking Powders ; Residue from Alum Baking Powders ; Objec- tions urged against Alum Powders ; Action of Baking Powders and Yeast Compared ; Keeping Qualities of Baking Powders ; Inspection of Baking Powders ; Fillers ; Home-made Baking Powders. CHAPTER XIII Vinegar, Spices, and Condiments 193 Vinegar ; Chemical Changes during Manufacture of Vinegar ; Ferment Action ; Materials used in Preparation of Vinegars ; Characteristics of a Good Vinegar ; Vinegar Solids ; Acidity of Vinegar ; Different Kinds of Vinegars ; Standards of Purity ; Adulteration of Vinegar ; Character- istics of Spices ; Pepper ; Cayenne ; Mustard ; Ginger ; Cinnamon and Cassia; Cloves; Allspice; Nutmeg; Adul- teration of Spices and Condiments; Essential Oils of; Uses of Condiments in Preparation of Foods ; Action of Condiments upon Digestion; Condiments and Natural Flavors. CHAPTER XIV Tea, Coffee, Chocolate, and Cocoa .... 203 Tea ; Sources of Tea Supply ; Composition of Tea ; Black Tea and Green Tea ; Judging Teas ; Adulteration of Tea ; Food Value and Physiological Properties of Tea ; CONTENTS Xlll PAGE Composition of Coffee ; Adulteration of Coffee ; Chicory in Coffee ; Glazing of Coffee ; Cereal Coffee Substitutes ; Cocoa and Chocolate Preparations ; Composition of Cocoa ; Chocolate ; Cocoa Nibs ; Plain Chocolate ; Sweet Choco- late ; Cocoa Butter ; Nutritive Value of Cocoa ; Adultera- tion of Chocolate and Cocoa ; Comparative Composition of Beverages. CHAPTER XV The Digestibility of Foods 214 Digestibility, how Determined ; Completeness and Ease of Digestion Process ; Example of Digestion Experiment ; Available Nutrients ; Available Energy ; Caloric Value of Foods ; Normal Digestion and Health ; Digestibility of Animal Foods ; Digestibility of Vegetable Foods ; Factors influencing Digestion ; Combination of Foods ; Amount of Food ; Method of Preparation of Food ; Mechanical Condition of Foods ; Mastication ; Palatability of Foods ; Physiological Properties of Foods ; Individuality ; Psy- chological Factors. CHAPTER XVI Comparative Cost and Value of Foods . . .231 Cost and Nutrient Content of Foods ; How to compare Two Foods as to Nutritive Value ; Cheap Foods ; Expen- sive Foods ; Nutrients Procurable for a Given Sura ; Ex- amples ; Comparing Nutritive Value of Common Foods at Different Prices ; Cost and Value of Nutrients. CHAPTER XVII Dietary Studies 244 Object of Dietary Studies ; Wide and Narrow Rations; Dietary Standards; Number of Meals per Day; Mixed XIV CONTENTS PAGE Dietary Desirable ; Animal and Vegetable Foods ; Economy of Production ; Food Habits ; Underfed Fami- lies ; Cheap and Expensive Foods ; Food Notions ; Dietary of Two Families Compared ; Food in its Relation to Mental and Physical Vigor; Dietary Studies in Public Institutions. CHAPTER XVIII Rational Feeding of Man 261 Object ; Human and Animal Feeding Compared ; Stand- ard Rations ; Why Tentative Dietary Standards ; Amounts of Food Consumed ; Average Composition of Foods ; Variations in Composition of Foods ; Example of a Ra- tion ; Calculations of Balanced Rations ; Requisites of a Balanced Ration ; Examples ; Calculations of Rations for Men at Different Kinds of Labor. CHAPTER XIX Water ... 268 Importance; Impurities in Water ; Mineral Impurities; Organic Impurities ; Interpretation of a Water Analysis ; Natural Purification of Water ; Water in Relation to Health; Improvement of Waters ; Boiling of Water ; Fil- tration ; Purification of Water by Addition of Chemicals ; Ice ; Rain Waters ; Waters of High and Low Purity ; Chemical Changes which Organic Matter of Water Un- dergoes ; Bacterial Content of Water; Mineral Waters; Materials for Softening Water ; Uses of; Economic Value of a Pure Water Supply. CHAPTER XX Food as affected by Household Sanitation and Storage ... . 284 Injurious Compounds in Foods ; Nutrient Content and CONTENTS XV PAGE Sanitary Condition of Food ; Sources of Contamination of Food ; Unclean Ways of Handling Food ; Sanitary In- spection of Food ; Infection from Impure Air ; Storage of Food in Cellars ; Respiration of Vegetable Cells ; Sun- light, Pure Water, and Pure Air as Disinfectants ; Foods contaminated from Leaky Plumbing ; Utensils for Storage of Food ; Contamination from Unclean Dishcloths ; Re- frigeration; Chemical Changes that take Place in the Refrigerator; Soil; Disposal of Kitchen Refuse; Germ Diseases spread by Unsanitary Conditions around Dwell- ings due to Contamination of Food ; General Considera- tions ; Relation of Food to Health. CHAPTER XXI Laboratory Practice 299 Object of Laboratory Practice ; Laboratory Note-book and Suggestions for Laboratory Practice ; List of Appara- tus Used ; Photograph of Apparatus Used ; Directions for Weighing ; Directions for Measuring ; Use of Micro- scope ; Water in Flour ; Water in Butter ; Ash in Flour ; Nitric Acid Test for Nitrogenous Organic Matter ; Acidity of Lemons ; Influence of Heat on Potato Starch Grains ; Influence of Yeast on Starch Grains ; Mechanical Compo- sition of Potatoes ; Pectose from Apples ; Lemon Extract ; Vanilla Extract ; Testing Olive Oil for Cotton Seed Oil ; Testing for Coal Tar Dyes ; Determining the Per Cent of Skin in Beans ; Extraction of Fat from Peanuts ; Micro- scopic Examination of Milk ; Formaldehyde in Cream or Milk ; Gelatine in Cream or Milk ; Testing for Oleomarga- rine ; Testing for Watering or Skimming of Milk ; Boric Acid in Meat ; Microscopic Examination of Cereal Starch Grains ; Identification of Commercial Cereals ; Granula- tion and Color of Flour ; Capacity of Flour to absorb XVI CONTENTS PAGE Water ; Acidity of Flour ; Moist and Dry Gluten ; Gliadin from Flour ; Bread-making Test ; Microscopic Examina- tion of Yeast ; Testing Baking Powders for Alum ; Test- ing Baking Powders for Phosphoric Acid ; Testing Baking Powders for Ammonia ; Vinegar Solids ; Specific Gravity of Vinegar ; Acidity of Vinegar ; Deportment of Vinegar with Reagents ; Testing Mustard for Turmeric ; Examina- tion of Tea Leaves ; Action of Iron Compounds upon Tannic Acid ; Identification of Coffee Berries ; Detecting Chicory in Coffee ; Comparative Amounts of Soap Neces- sary with Hard and Soft Water ; Solvent Action of Water on Lead ; Suspended Matter in Water ; Organic Matter in Water ; Deposition of Lime by Boiling Water ; Quali- tative Tests for Minerals in Water; Testing for Nitrites in Water. Review Questions 323 References 350 Index 357 HUMAN FOODS AND THEIR NUTRITIVE VALUE HUMAN FOODS AND THEIR NUTRITIVE VALUE CHAPTER I GENERAL COMPOSITION OF FOODS 1. Water. — All foods contain water. Vegetables in their natural condition contain large amounts, often 95 per cent, while in meats there is from 40 to 60 per cent or more. Prepared cereal products, as flour, corn meal, and oatmeal, which are apparently dry, have from 7 to 14 per cent. In general the amount of water in a food varies with the mechanical structure and the conditions under which it has been prepared, and is an important factor in estimating the value, as the nutrients are often greatly decreased because of large amounts of water. The water in substances as flour and meal is mechani- cally held in combination with the fine particles and varies with the moisture content, or hydroscopicity, of the air. Oftentimes foods gain or lose water to such an extent as to affect their weight; for example, one hundred pounds of flour containing 12 per cent of water may be reduced in weight three pounds or more when stored in a dry place, or there may be an increase B I 2 HUMAN FOODS AND THEIR NUTRITIVE VALUE in weight from being stored in a damp place. In tables of analyses the results, unless otherwise stated, are usually given on the basis of the original material, or the dry substance. Potatoes, for example, contain- 2j per cent of crude protein on the basis of 75 per cent of water; or on a dry matter basis, that is, when the water is entirely eliminated, there is 10 per cent of protein. The water of foods is determined by drying the weighed material in a water or air oven at a tempera- ture of about 100° C., until all of the moisture has been expelled in the form of steam, leaving the dry matter or material free from water.^ The determination of dry matter, while theoretically a simple process, is attended with many difficulties. Substances which contain much fat may undergo o.xidation during drying; volatile com- pounds, as essential oils, are expelled along with the moisture; and other changes may occur affecting the accuracy of the work. The last traces of moisture are removed with difficulty from a substance, being me- chanically retained by the particles with great tenacity. When very accurate dry matter determinations are de- sired, the substance is dried in a vacuum oven, or in a desiccator over sulphuric acid, or in an atmosphere of some non-oxidizing gas, as hydrogen. 2. Dry Matter. — The dry matter of a food is a me- chanical mixture of the various compounds, as starch, sugar, fat, protein, cellulose, and mineral matter, and is GENERAL COMPOSITION OF FOODS Fig. I. — Apparatus used for the Determination of Dry Matter AND Ash in Foods. I, desiccator; 2, muffle furnace for combustion of foods and obtaining ash; 3, water oven for drying food materials. obtained by drying the material. Succulent vegetable foods with 95 per cent of water contain only 5 per cent 4 HUMAN FOODS AND THEIR NUTRITIVE VALUE of dry matter, while in flour with 12 per cent of water there is 88 per cent, and in sugar 99 per cent. The dry matter is obtained by subtracting the per cent of water from 100, and in foods it varies from 5 per cent and less in some vegetables to 99 per cent in sugar. 3. Ash. — The ash, or mineral matter, is that portion obtained by burning or igaiting the dry matter at the lowest temperature necessary for complete combustion. The ash in vegetable foods ranges from 2 to 5 per cent and, together with the nitrogen, represents what was taken from the soil during growth. In animal bodies, the ash is present mainly in the bones, but there is also an appreciable amount, one per cent or more, in all the tissues. Ash is exceedingly variable in composition, being composed of the various salts of potassium, so- dium, calcium, magnesium, and iron, as sulphates, phos- phates, chlorides, and silicates of these elements. There are also other elements in small amounts. In the plant economy these elements take an essential part and are requisite for the formation of plant tissue and the pro- duction in the leaves of the organic compounds which later are stored up in the seeds. Some of the elements appear to be more necessary than others, and whenever withheld plant growth is restricted. The elements most essential for plant growth are potassium, calcium, magnesium, iron, phosphorus, and sulphur. ^ In the animal body minerals are derived, either di- rectly or indirectly, from the vegetable foods consumed. GENERAL COMPOSITION OF FOODS 5 The part which each of the mineral elements takes in animal nutrition is not well understood. Some of the elements, as phosphorus and sulphur, are in organic combination with the nitrogenous compounds, as the nucleated albuminoids, which are very essential for ani- mal life. In both plant and animal bodies, the mineral matter is present as mineral salts and organic combina- tions. It is held that the ash elements which are in organic combination are the fornis mainly utilized for tissue construction. While it is not known just what part all the mineral elements take in animal nutrition, experiments show that in all ordinary mixed rations the amount of the different mineral elements is in excess of the demands of the body, and it is only in rare instances, as in cases of restricted diet, or convalescence from some disease, that special attention need be given to increasing the mineral content of the ration. An ex- cess of mineral matter in foods is equally as objection- able as a scant amount, elimination of the excess entail- ing additional work on the body. The composition of the ash of different food mate- rials varies widely, both in amount, and form of the individual elements. When for any reason it is neces- sary to increase the phosphates in a ration, milk and eggs do this to a greater extent than almost any other foods. Common salt, or sodium chloride, is one of the most essential of the mineral constituents of the body. It is necessary for giving the blood its normal composi- tion, furnishing acid and basic constituents for the pro- 6 HUMAN FOODS AND THEIR NUTRITIVE VALUE duction of the digestive fluids, and for the nutrition of the cells. While salt is a necessary food, in large amounts, as when the attempt is made to use sea water as a beverage, it acts as a poison, suggesting that a ma- terial may be both a food and a poison. When sodium chloride is entirely withheld from an animal, death from salt starvation ensues. Many foods contain natu- rally small amounts of sodium chloride. 4. Organic Matter. ■ — ■ That portion of a food material which is converted into gaseous or volatile products during combustion is called the organic matter. It is a mechanical mixture of compounds made up of car- bon, hydrogen, oxygen, nitrogen, and sulphur, and is composed of various individual organic compounds, as cellulose, starch, sugar, albumin, and fat. The amount in a food is determined by subtracting the ash and water from lOO. The organic matter varies widely in composition ; in some foods it is largely starch, as in potatoes and rice, while in others, as forage crops con- sumed by animals, cellulose predominates. The na- ture of the prevailing organic compound, as sugar or starch, determines the nutritive value of a food. Each has a definite chemical composition capable of being expressed by a formula. Considered collectively, the organic compounds are termed organic matter. When burned, the organic compounds are converted into gases, the carbon uniting with the oxygen of the air to form carbon dioxide, hydrogen to form water, sul- GENERAL COMPOSITION OF FOODS 7 phur to form sulphur dioxide, and the nitrogen to form oxides of nitrogen and ammonia. 5. Classification of Organic Compounds. — All food materials are composed of a large number of organic compounds. For purposes of study these are divided into classes. The element nitrogen is taken as the basis of the division. Compounds which contain this element are called nitrogenous, while those from which it is absent are called non-nitrogenous.^ The nitroge- nous organic compounds are composed of the elements nitrogen, hydrogen, carbon, oxygen, and sulphur, while the non-nitrogenous compounds are composed of carbon, hydrogen, and oxygen. In vegetable foods the non- nitrogenous compounds predominate, there being usually from six to twelve parts of non-nitrogenous to every one part of nitrogenous, while in animal foods the nitroge- nous compounds are present in larger amount. NON-NITROGENOUS COMPOUNDS 6. Occurrence. — The non-nitrogenous compounds of foods consist mainly of cellulose, starch, sugar, and fat. For purposes of study, they are divided into subdivi- sions, as carbohydrates, pectose substances or jellies, fats, organic acids, essential oils, and mixed compounds. In plants the carbohydrates predominate, while in ani- mal tissue the fats are the chief non-nitrogenous con- stituents. 8 HUMAN FOODS AND THEIR NUTRITIVE VALUE 7. Carbohydrates. — This term is applied to a class of compounds similar in general composition, but dif- fering widely in structural composition and physical properties. Carbohydrates make up the bulk of vege- table foods and, except in milk, are found only in traces in animal foods. They are all represented by the general formula CH^^O,,, there being twice as many hydrogen as o.xygen atoms, the hydrogen and oxygen being present in the same proportion as in water. As a class, the carbohydrates are neutral bodies, and, when burned, form carbon dioxide and water. 8. Cellulose is the basis of the cell structure of plants, and is found in various physical forms in food ma- terials.^ Sometimes it is hard and dense, resisting digestive action and mechanically inclosing other nutri- ents and thus preventing their being available as food. In the earlier stages of plant growth a part of the cellulose is in chemical combination with water, forming hydrated cellu- lose, a portion of which undergoes digestion and produces heat and en- ergy in the body. Ordinarily, how- FiG. 2. — CELT.tii.AR ever, cellulose adds but little in the Structure of way of nutritive value, although it is Plant Cell. often beneficial mechanically and im- parts bulk to some foods otherwise too concentrated. The mechanical action of cellulose on the digestion of GENERAL COMPOSITION OF FOODS 9 food is discussed in Chapter XV. Cellulose usually makes up a very small part of human food, less than i jjer cent. In refined white flour there is less than .05 of a per cent; in oatmeal and cereal products from .5 to I per cent, depending upon the extent to which the hulls are removed, and in vegetable foods from .1 to I per cent. The cellulose content of foods is included in the crude fiber of the chemist's report. \ 9. Starch occurs widely distributed in nature, par- ticularly in the seeds, roots, and tubers of some plants. It is formed in the leaves of plants as a result of the joint action of chlorophyll and protoplasm, and is gen- erally held by plant physiologists to be the first com- pound produced in. the plant cell. Starch is composed of a number of overlapping layers separated by starch cellulose ; between these layers the true starch or amy- lose is found. Starch from the various cereals and vegetables differs widely in mechanical structure ; in wheat it is circular, in corn somewhat angular, and in parsnips exceedingly small, while potato starch granules are among the largest* The nature of starch can be determined largely from its mechanical structure as studied under the microscope. It is insoluble in cold water because of the protecting action of the cellular layer, but on being heated it undergoes both mechanical and chemical changes ; the grains are partially ruptured by pressure due to the conversion into steam of the moisture held mechanically. The cooking of foods is lO HUMAN FOODS AND THEIR NUTRITIVE VALUE beneficial from a mechanical point of view, as it results in partial disintegration of the starch masses, changing the structure so that the starch is more readily acted upon by the ferments of the digestive tract. At a temperature of about 120° C. starch begins to undergo chemical change, resulting in the rearrangement of the atoms in the molecule with the production of dextrine and soluble carbohydrates. Dextrine is formed on the crust of bread, or whenever potatoes or starchy foods are browned. At a still higher temperature starch is decomposed, with the liberation of water and production of compounds of higher carbon content. When heated in contact with water, it undergoes hydration changes ; gelati- nous-like products are formed, which are finally converted into a soluble condition. In cooking cereals, the hydra- tion of the starch is one of the main physical and chemical changes that takes place, and it simply results in converting the material into such a form that other chemical changes may more readily occur. Before starch becomes dextrose, hydration is necessary. If this is accomplished by cooking, it saves the body just so much energy in digestion. Many foods owe their value largely to the starch. In cereals it is found to the extent of 72 to 76 per cent ; in rice and potatoes in % still larg er amounts ; and it is the chief constituent of many vegetables. When starch is digested, it is first changed to a soluble form and then gradually undergoes oxidation, resulting in the production of heat and energy, the same products — carbon dioxide and water — being GENERAL COMPOSITION OF FOODS II formed as when starch is burned. Starch is a valu- able heat-producing nutrient; a pound yields i860 calories. See Chapter XV, 10. Sugar. — Sugars are widely distributed in nature, being found principally in the juices of the sugar cane, sugar beet, and sugar maple. They are divided into two large classes : the sucrose group and the dextrose group, the latter being produced from sucrose, starch, and other carbohydrates by inversion and allied chemi- cal changes. Because of the importance of sugar in the dietary. Chapter V is devoted to the subject. 11. Pectose Substances are jelly-like bodies found in fruits and vegetables. They are closely related in chemical composition to the carbohydrates, into which form they are changed during digestion ; and in nutri- tion they serve practically the same function. In the early stages of growth the pectin bodies are combined with organic acids, forming insoluble compounds, as the pectin in green apples. During the ripening of fruit and the cooking of vegetables, the pectin is changed to a more soluble and digestible condition. In food analy- sis, the pectin is usually included with the carbohy- drates. 12. Nitrogen-free-extract. — In discussing the com- position of foods, the various non-nitrogenous com- pounds, as starch, sugar, and pectin, are grouped under the name of nitrogen-free-extract. Methods of chemi- 12 HUMAN FOODS AND THEIR NUTRITIVE VALUE cal analysis have not yet been sufficiently perfected to enable accurate and rapid determination to be made of all these individual carbohydrates, and hence they are grouped together as nitrogen-free-extract. As the name indicates, they are compounds which contain no nitrogen, and are extractives in the sense that they are soluble in dilute acid and alkahne solutions. The nitro- gen-free-extract is determined indirectly, that is, by the method of difference. All the other constituents of a food, as water, ash, crude fiber (cellulose), crude protein, and ether extract, are determined ; the total is subtracted from loo, and the difference is nitrogen -free-extract. In studying the nutritive value, of foods, particular attention should be given to the nature of the nitrogen- free-extract, as in some instances it is composed of sugar and in others of starch, pectin, or pentosan (gum sugars). While all these compounds have practically the same fuel value, they differ in composition, struc- ture, and the way in which they are acted upon by chemicals and digestive ferments.-' 13. Fat. — Fat is found mainly in the seeds of plants, but to some extent in the leaves and stems. It differs from starch in containing more carbon and less oxygen. In starch there is about 44 per cent of carbon, while in fat there is 75 per cent. Hence it is that when fat is burned or undergoes combustion, it yields a larger amount of the products of combustion — carbon dioxid and water — than does starch. A gram of fat produces GENERAL COMPOSITION OF FOODS 13 2^ times as much heat as a gram of starch. Fat is the most concentrated non-nitrogenous nutrient. As found in food mate- rials, it is a mechani- cal mixture of various fats, among which are stearin, palmitin, and olein. Stearin and palmitin are hard fats, crystalline in struc- ture, and with a high melting point, while olein is a liquid. In ad- dition to these three, there are also small amounts of other fats, as butyrin in butter, which give character or individuality to ma- terials. There are a number of vegetable fats or oils which are used for food pur- poses and, when prop- erly prepared and refined, have a high fig. 3. — apparatus used forthe deter- nutritive value. Occa- ' minat.on ok fat. sionally one fat of cheaper origin but not necessarily of lower nutritive value is substituted for another. The 14 HUMAN FOODS AND THEIR NUTRITIVE VALUE fats have definite physical and chemical properties which enable them to be readily distinguished, as iodine num- ber, specific gravity, index of refraction, and heat of com- bustion. By iodine number is meant the percentage of iodine that will unite chemically with the fat. Wheat oil has an iodine number of about lOO, meaning that one pound of wheat oil will unite chemically with one pound of iodine. Fats have a lower specific gravity than water, usually ranging from .89 to .94, the specific gravity of a fat being fairly constant. All fats can be separated into glycerol and a fatty acid, glycerol or glycerine being common constituents, while each fat yields its own characteristic acid, as stearin, stearic acid ; palmitin, palmitic acid ; and olein, oleic acid. The fats are soluble in ether, chloroform, and benzine. In the chemical analysis of foods, they are separated with ether, and along with the fat, variable amounts of other substances are extracted, these extractive products usually being called "ether extract" or "crude fat." ^ The ether extract of plant tissue contains in addition to fat appreciable amounts of cellulose, gums, coloring, and other materials. From cereal products the ether extract is largely fat, but in some instances lecithin and other nitrogenous fatty substances are present, while in animal food products, as milk and meat, the ether extract is nearly pure fat. 14. Organic Acids. — Many vegetable foods contain small amounts of organic acids, as malic acid found in GENERAL COMPOSITION OF FOODS 15 apples, citric in lemons, and tartaric in grapes. These give characteristic taste to foods, but have no direct nutritive value. They do not yield heat and energy as do starch, fat, and protein ; they are, however, useful for imparting flavor and palatability, and it is believed they promote to some extent the digestion of foods with which they are combined by encouraging the secretion of the digestive fluids. Many fruits and vegetables owe their dietetic value to the organic acids which they con- tain. In plants they are usually in chemical combina- tion with the minerals, forming compounds as salts, or with the organic compounds, producing materials as acid proteins. In the plant economy they take an essential part in promoting growth and aiding the plant to secure by osmotic action its mineral food from the soil. Organic acids are found to some extent in animal foods, as the various lactic acids of meat and milk. They are also formed in food materials as the result of ferment action. When seeds germinate, small amounts of carbohydrates are converted into organic acids. In general the organic acids are not to be considered as nutrients, but as food adjuncts, increasing palatability and promoting digestion. 15. Essential Oils. — Essential or volatile oils differ from fats, or fixed oils, in chemical composition and physical properties.^ The essential oils are readily volatilized, leaving no permanent residue, while the fixed fats are practically non-volatile. Various essen- 1 6 HUMAN FOODS AND THEIR NUTRItlVE VALUE tial oils are present in small amounts in nearly all vegetable food materials, and the characteristic flavor of many fruits is due to them. It is these compounds which are used for flavoring purposes, as discussed in Chapter IV. The amount in a food material is very small, usually only a few hundredths of a per cent. The essential oils have no direct food value, but in- directly, like the organic acids, they assist in promoting favorable digestive action, and are also valuable because they impart a pleasant taste. Through poor methods of cooking and preparation, the essential oils are readily lost from some foods. 16. Mixed Compounds. — Food materials frequently contain compounds which do not naturally fall into the five groups mentioned, — carbohydrates, pectose sub- stances, fats, organic acids, and essential oils. The amount of such compounds is small, and they are classed as miscellaneous or mixed non-nitrogenous compounds. Some of them may impart a negative value to the food, and there are others which have all the characteristics, as far as general composition is concerned, of the non- nitrogenous compounds, but contain nitrogen, although as a secondary rather than an essential constituent. 17. Nutritive Value of Non-nitrogenous Compounds. — The non-nitrogenous compounds, taken as a class, are incapable alone of sustaining life, because they do not contain any nitrogen, and this is necessary for produc- GENERAL COMPOSITION OF FOODS 1 7 ing proteid material in ttie animal body. They are valuable for the production of heat and energy, and when associated with the nitrogenous compounds, are capable of forming non-nitrogenous reserve tissue. It is equally impossible to sustain life for any prolonged period with the nitrogenous compounds alone. It is when these two classes are properly blended and naturally united in food materials that their main value is secured. For nutrition purposes they are mutually related and dependent. Some food materials contain the nitrogenous and non-nitrogenous compounds blended in such proportion as to enable one food alone to prac- tically sustain life, while in other cases it is necessary, in order to secure the best results in the feeding of animals and men, to combine different foods varying in their content of these two classes of compounds.' NITROGENOUS COMPOUNDS 18. General Composition. — The nitrogenous com- pounds are more complex in composition than the non- nitrogenous. They are composed of a larger number of elements, united in different ways so as to form a much more complex molecular structure. Foods con- tain numerous nitrogenous organic compounds, which, for purposes of study, are divided into four divisions, — proteids, albuminoids, amids, and alkaloids. In addition to these, there are other nitrogenous compounds which do not naturally fall into any one of the four divisions. l8 HUMAN FOODS AND THEIR NUTRITIVE VALUE Fig, 4. -Apparatus used for Determinmnc Total Nitrogen and Cki:i)E Protein in Fuohs. The material is digested in the flask (3) with sulphu' ic acid and the organic nitrogen converted into ammonium sulphate, which is later liberated and distilled at i, and the ammonia neutralized with stamlard acid (2), GENERAL COMPOSITION OF FOODS 1 9 Also in some foods there are small amounts of nitrogen in mineral forms, as nitrates and nitrites. 19. Protein. — The term "protein" is applied to a large class of nitrogenous compounds resembling each other in general composition, but differing widely in structural composition. As a cl^ss, the proteins contain about i6 per cent of nitrogen, 52 per cent of carbon, from 6 to 7 per cent of hydrogen, 22 per cent of oxygen, and less than 2 per cent of sulphur. These elements are com- bined in a great variety of ways, forming various groups or radicals. In studying the protein molecule a large number of derivative products have been observed, as amid radicals, various hydrocarbons, fatty acids, and carbohydrate-like bodies.^ It would appear that in the chemical composition of the proteins there are all the constituents, or simpler products, of the non-nitrogenous compounds, and these are in chemical combination with amid radicals and nitrogen in various forms. The nitro- gen of many proteids appears to be present in more than one form or radical. The proteids take an im- portant part in life processes. They are found more extensively in animal than in plant bodies. The pro- toplasm of both the plant and animal cell is composed mainly of protein. Proteids are divided into various subdivisions, as albumins, globulins, albuminates, proteoses and pep- tones, and insoluble proteids. In plant and animal foods a large amount of the protein is present as in- 20 HUMAN FOODS AND THEIR NUTRITIVE VALUE soluble proteids ; that is, they are not dissolved by sol- vents, as water and dilute salt solution. The albumins are soluble in water and coagulated by heat at a tem- perature of 157° to 161° F. Whenever a food material is soaked in water, the albumin is removed and can then be coagulated by the action of heat, or of chemi- cals, as tannic acid, lead acetate, and salts of mercury. The globulins are proteids extracted from food materials by dilute salt solution after the removal of the albumins. Globulins also are coagulated by heat and precipitated by chemicals. The amount of globulins in vegetable foods is small. In animal foods myosin and vitellin, found in the yolk of the egg, and some of the proteids of the blood, are examples of globulins. Albuminates are casein-like proteids found in both animal and vege- table foods. They are supposed to be proteins that are in feeble chemical combination with acid and alkaline compounds, and they are sometimes called acid and alkali proteids. Some are precipitated from their solu- tions by acids and others by alkalies. Peas and beans contain quite large amounts of a casein-like proteid called legumin. Proteoses and peptones are proteins soluble in water, but not coagulated bv heat. They are- produced from other proteids by ferment action during the digestipn of food and the germination of seeds, and are often due to the changes resulting from the action of the natural ferments or enzymes inherent in the food materials. As previously stated, the insolu- ble proteids are present in far the largest amount of any GENERAL COMPOSITION OF FOODS 21 of the nitrogenous materials of foods. Lean meat and the ghiten of wheat and other grains are examples of the insoluble proteids. The various insoluble proteids from different food materials each has its own compo- sition and distinctive chemical and physical properties, and from each a different class and percentage amount of derivative products are obtained. ^ While in general it is held that the various proteins have practically the same nutritive value, it is possible that because of differ- ences in structural composition and the products formed during digestion there may exist notable differences in nutritive value. During digestion the insoluble pro- teids undergo an extended series of chemical changes. They are partially oxidized, and the nitrogenous portion of the molecule is eliminated mainly in the form of amids, as urea. The insoluble proteins constitute the main source of the nitrogenous food supply of both humans and animals. 20. Crude Protein. — In the analysis of foods, the term " crude protein " is used to designate the total nitrogenous compounds considered collectively ; it is composed largely of protein, but also includes the amids, alkaloids, and albuminoids. " Crude protein " and "total nitrogenous compounds" are practically synonymous terms. The various proteins all contain about i6 per cent of nitrogen ; that is, one part of nitro- gen is equivalent to 5.25 parts of protein. In analyzing a food material, the total organic nitrogen is determined 22 HUMAN FOODS AND THEIR NUTRITIVE VALUE and the amount multiplied by 6.25 to obtain the crude protein. In some food materials, as cereals, the crude protein is largely pure protein, while in others, as pota- toes, it is less than half pure protein, the larger portion being amids and other compounds. In comparing the crude protein content of one food with that of another, the nature of both proteids should be considered and also the amounts of non-proteid constituents. The factor 6.25 for calculating the protein equivalent of foods is not strictly applicable to all foods. For example, the proteids of wheat — gliadin and glutenin — contain over 18 per cent of nitrogen, making the nitrogen factor about 5.68 instead of 6.25. If wheat contains 2 per cent of nitrogen, it is equivalent to 12.5 per cent of crude protein, using the factor 6.25 ; or to 11.4, using the factor 5.7. The nitrogen content of foods is abso- lute ; the protein content is only relative.^ 21. Food Value of Protein. — Because of its complex- ity in composition, protein is capable of being used by the body in a greater variety of ways than starch, sugar, or fat. In addition to producing heat and energy, pro- tein serves the unique function of furnishing material for the construction of new muscular tissue and the repair of that which is worn out. It is distinctly a tissue-build- ing nutrient. It also enters into the composition of all the vital fluids of the body, as the blood, chyme, chyle, and the various digestive fluids. Hence it is that pro- tein is required as a nutrient by the animal body, and it GENERAL COMPOSITION OF FOODS 23 cannot be produced from non-nitrogenous compounds. In vegetable bodies, the protein can be produced syn- thetically from amids, which in turn are formed from ammonium compounds. While protein is necessary in the ration, an excessive amount should be avoided. When there is more than is needed for functional pur- poses, it is used for heat and energy, and as foods rich in protein are usually the most expensive, an excess adds unnecessarily to the cost of the ration. Excess of pro- tein in the ration may also result in a diseased condition, due to imperfect elimination of the protein residual prod- ducts from the body.^'' 22. Albuminoids differ from proteids in general com- position and, to some extent, in nutritive value. They are found in animal bodies mainly in the connective tissue and in the skin, hair, and nails. Some of the albu- minoids, as nuclein, are equal in food value to protein, while others have a lower food value. In general, albuminoids are capable of conserving the protein of the body, and hence are called " protein sparers," but they cannot in every way enter into the composition of the body, as do the true proteins. 23. Amids and Amines. — These are nitrogenous compounds of simpler structure than the proteins and albuminoids. They are sometimes called compound ammonia in that they are derived from ammonia by the re- placement of one of the hydrogen atoms with an organic radical. In plants, amids are intermediate compounds 24 HUMAN FOODS AND THEIR NUTRITIVE VALUE in the production of the proteids, and in some vegetables a large portion of the nitrogen is amids. In animal bodies amids are formed during oxidation, digestion, and disintegration of proteids. It is not definitely known whether or not a protein in the animal body when broken down into amid form can again be reconstructed into protein. The amids have a lower food value than the proteids and albuminoids. It is generally held that, to a certain extent, they are capable, when combined with proteids, of preventing rapid conversion of the body proteid into soluble form. When they are used in large amounts in a ration, they tend to hasten oxida- tion rather than conservation of the proteids. 24. Alkaloids. — In some plant bodies there are small amounts of nitrogenous compounds called alkaloids. They are not found to any appreciable extent in food plants. The alkaloids, like ammonia, are basic in character and unite with acids to form salts. Many medicinal plants owe their value to the alkaloids which they contain. In animal bodies alkaloids are formed when the tissue undergoes fermentation changes, and also during disease, the products being known as ptomaines. Alkaloids have no food value, but act physiologically as irritants on the nerve centers, making them useful from a medicinal rather than from a nutri- tive point of view. To medical and pharmaceutical students the alkaloids form a very important group of compounds. GENERAL COMPOSITION OF FOODS 25 25. General Relationship of the Nitrogenous Com- pounds. — Among the various subdivisions of the nitroge- nous compounds there exists a relationship similar to that among the non-nitrogenous compounds. From I 2 3 4 5 fi Fig. 5. — Graphic Composition of Flour. I, flour; 2, starch; 3, gluten ; 4, water; 5, fat; 6, ash. proteids, amids and alkaloids may be formed, just as invert sugars and their products are formed from sucrose. Although glucose products are derived from sucrose, it is not possible to reverse the process and obtain sucrose or cane sugar from starch. So it is with proteins, while the amid may be obtained from the 26 HUMAN FOODS AND THEIR NUTRITIVE VALUE proteid in animal nutrition, as far as known the process cannot be reversed and proteids be obtained from amids. In the construction of the protein molecule of plants, nitrogen is absorbed from the soil in soluble forms, as compounds of nitrates and nitrites and ammonium salts. These are converted, first, into amids and then into proteids. In the animal body just the reverse of this process takes place, — the protein of the food under- goes a series of changes, and is finally eliminated from the body as an amid, which in turn undergoes oxidation and nitrification, and is converted into nitrites, nitrates, and ammonium salts. These forms of nitrogen are then ready to begin again in plant and animal bodies the same cycle of changes. Thus it is that nitrogen may enter a number of times into the composition of plant and animal tissues. Nature is very economical in her use of this element.^ chaptf:r II CHANGES IN COMPOSITION OF FOODS DURING COOK- ING AND PREPARATION 26. Raw and Cooked Foods Compared. — Raw and cooked foods differ in chemical composition mainly in the content of water. The amount of nutrients on a dry matter basis is practically the same, but the struc- tural composition is affected by cooking, and hence it is that a food prepared for the table often differs appreciably from the raw material. Cooked 'meat, for example, has not the same percentage and structural composition as raw meat, although the difference in nutritive value between a given weight of each is not large. During cooking, foods are acted upon chemi- cally, physically, and bacteriologically, and it is usually the joint action of these three agencies that brings about the desirable changes incident to their preparation for the table. 27. Chemical Changes during Cooking. — Each of the chemical compounds of which foods are composed is influenced to a greater or less extent by heat and modified in composition. The chemistry of cooking is mainly a study of the chemical changes that take place when compounds, as cellulose, starch, sugar, pectin, fat, 27 28 HUMAN FOODS AND THEIR NUTRITIVE VALUE and the various proteids, are subjected to the joint action of heat, moisture, air, and ferments. The changes which affect the cellulose are physical rather than chemical. A slight hydration of the cellular tissue, however, does take place. In human foods cellulose is not found to any appreciable extent. Many vegetables, as potatoes, which are apparently composed of cellular substances, contain but little true cellulose. Starch, as previously stated, undergoes hydration in the presence of water, and, at a temperature of 120° C, is converted into dextrine. At a higher temperature disintegration of the starch molecule takes place, with the formation of carbon monoxid, carbon dioxid, and water, and the production of a residue richer in carbon than is starch. On account of the moisture, the temperature in many cooking operations is not sufficiently high for changes other than hydration and preliminary dextrinizing. In Chapter XI is given a more extended account of the changes affecting starch which occur in bread making. During the cooking process sugars undergo inversion to a slight extent. That is, sucrose is converted into levulose and dextrose sugars. At a higher temperature, sugar is broken up into its constituents — water and carbon dioxide. The organic acids which many fruits and vegetables contain hasten the process of inversion. When sugar is subjected to dry heat, it becomes a brown, caramel-like material sometimes called barley sugar. During cooking, sugars are not altered in solubility or digestibility ; starches, however, are changed to a more CHANGES IN FOODS DURING COOKING 29 soluble form, and pectin — a jelly-like substance — is converted from a less to a more soluble condition, as stated in Chapter I. Changes incident to the cooking of fruits and vegetables rich in pectin, as in the making of jellies, are similar to those which take place in the last stages of ripening. The fats are. acted upon to a considerable extent by heat. Some of the vegetable oils undergo slight oxida- tion, resulting in decreased solubility in ether, but since there is no volatilization of the fatty matter, it is a change that does not materially affect the total fuel value of the food.^^ There is a general tendency for the proteids to be- come less soluble by the action of heat, particularly the albumins and globulins. The protein molecule dissoci- ates at a high temperature, with formation of volatile, products, and therefore foods rich in protein should not be subjected to extreme heat, as losses of food value may result. During cooking, proteids undergo hydra- tion, which is necessary and preliminary to digestion, and the heating need be carried only to this point, and not to the splitting up of the molecule. Prolonged high temperature in the cooking of proteids and starches is unnecessary in order to induce the desired chemical changes. When these nutrients are hydrated, they are in a condition to undergo digestion, without the body being compelled to expend unnecessary energy in bring- ing about this preliminary change. Hence it is that, while proper cooking does not materially affect the total 30 HUMAN FOODS AND THEIR NUTRITIVE VALUE digestibility of proteids or starches, it influences ease of digestion, as well as conserves available energy, thereby making more economical use of these nutrients. 28. Physical Changes. — The mechanical structure of foods is influenced by cooking to a greater extent than is the chemical composition. One of the chief objects of cooking is to bring the food into better mechanical condition for digestion. ^^ Heat and water cause partial disintegration of both animal and vegetable tissues. The cell-cementing materials are weakened, and a sof- tening of the tissues results. Often the action extends still further in vegetable foods, resulting in disintegration of the individual starch granules. When foods are subjected to dry heat, the mois- ture they contain is converted into steam, which causes bursting of the tis- sues. A good ex- ample of this is the popping of corn. Heat may result, too, in mechanical removal of some of the nutrients, as the fats, which are liquefied at temperatures Fig. 6. — Cells of a Partially Cooked Potato. (After Kiixii;.) CHANGES IN FOODS DURING COOKING 31 ranging from 100° to 200° F. Many foods which in the raw state contain quite large amounts of fat, lose a por- tion mechanically during cooking, as is the case with bacon when it is cut in thin slices and fried or baked until crisp. When foods are boiled, the natural juices being of somewhat different density from the water in which they are cooked, slight osmotic changes occur. There is a tendency toward equalization of the compo- sition of the juices of the food and the water in which they are cooked. In order to achieve the best mechani- cal effects in cooking, high temperatures are not neces- sary, except at first for rupturing the tissues ; softening of the tissues is best effected by prolonged and slow heat. At a higher temperature many of the volatile and essential oils are lost, while at lower temperatures these are retained and in some instances slightly developed. The cooking should be sufficiently pro- longed and the tem- perature high enough to effectually disintegrate and soften all of the tissues but not to cause extended chemical changes. Fig. 7. — CELts OF Raw Potato, showing Starch Grains, (.^fier Konig.) 32 HUMAN l-'OODS AND THEIR NUTRITIVE VALUE There is often an unnecessarily large amount of heat lost through faulty construction of stoves and lack of judicious use of fuels, which greatly enhances the cost of preparing foods. Ovens are frequently coated with deposits of soot ; this causes the heat to be thrown out into the room or lost through the chimney, rather than utilized for heating the oven. In an ordinary cook stove it is estimated that less than 7 per cent of the heat and energy of the fuel is actually employed in bringing about physical and chemical changes incident to cooking.^^ 29. Bacteriological Changes. — The bacterial organ- isms of foods are destroyed in the cooking, provided a temperature of 150° F. is reached and maintained for several minutes. The interior of foods rarely reaches a temperature above 200° F-, because of the water they contain which is not completely removed below 212°. One of the chief objects in cooking food is to render it sterile. Not only do bacteria become innocuous through cooking, but various parasites, as trichina and tapeworm, are destroyed, although some organisms can live at a comparatively high temperature. Cooked foods are easily re-inoculated, in some cases more readily than fresh foods, because they are in a more disintegrated condition. In many instances bacteria are of material assistance in the preparation of foods, as in bread making, butter making, curing of cheese, and ripening of meat. All the chemical compounds of which foods are composed CHANGES IN FOODS DURING COOKING 33 are subject to fermentation, each compound being acted upon by its special ferment body. Those which convert the proteids into soluble form, as the peptonizing fer- ments, have no action upon the carbohydrates. A cycle of bacteriological changes often takes place in a food material, one class of ferments working until their prod- ucts accumulate to such an extent as to prevent their further activity, and then the process is taken up by others, as they find the conditions favorable for devel- opment. This change of bacterial flora in food mate- rials is akin to the changes in the vegetation occupying soils. In each case, there is a constant struggle for possession. Bacteria take a much more important part in the preparation of foods than is generally considered. As a result of their workings, various chemical products, as organic acids and aromatic compounds, are produced. The organic acids chemically unite with the nutrients of foods, changing their composition and physical proper- ties. Man is, to a great extent, dependent upon bacterial action. Plant life also is dependent upon the bacterial changes which take place in the soil and in the plant tis- sues. The stirring of seeds into activity is apparently due to enzymes or soluble ferments which are inherent in the seed. A study of the bacteriological changes which foods undergo in their preparation and digestion more properly belongs to the subject of bacteriology, and in this work only brief mention is made of some of the more important parts which microorganisms take in the preparation of foods. 34 HL'IIAN FOODS AND THEIR NUTRITIVE VALUE 30. Insoluble Ferments. — Insoluble ferments are mi- nute, plant-like bodies of definite form and structure, and can be studied only with the micro- ^ .^ ^^ ^\ scope. 1 They are developed from ^^S'«»»^'*% spores or seeds, or from the split- I ting or budding of the parent cells. Under suitable conditions they mul- FiG. 8.-LAcn.; Acid ^'P^^ ''^1^^'^^^' deriving the energy for Bacteria, much their Hfe processes from the chemical RukeTi!"' ^'^^"' changes which they induce. For ex- ample, in the souring of milk the milk sugar is changed by the lactic acid ferments into lactic acid. In causing chemical changes, the ferment gives none of its own material to the reacting substance. These ferment bodies undergo life processes similar to plants of a higher order. All foods contain bacteria or ferments. In fact, it is impossible for a food stored and prepared under ordi- nary conditions, unless it has been specially treated, to be free from them. Some of them are useful, some are injurious, while others are capable of producing disease. The objectionable bacteria are usually destroyed by the joint action of sunlight, pure air, and water. 31. Soluble Ferments. — Many plant and animal cells have the power of secreting substances soluble in water and capable of producing fermentation changes ; to these the term "soluble ferments," or "enzymes," is appHed. These ferments have a cell structure like the CHANGES IN FOODS DURING COOKING 35 organized ferments. When germinated seed, as malted barley, is extracted, a soluble and highly nitrogenous substance, called the diastase ferment, is secured that changes starch into soluble forms. The soluble fer- ments induce chemical change by causing molecular disturbance or splitting up of the organic compounds, resulting in the production of derivative products. They take an important part in animal and plant nutrition, as by their action insoluble compounds are brought into a soluble condition so they can be utilized for nutritive purposes. In many instances ferment changes are due to the joint action of soluble and insoluble ferments. The insoluble ferment secretes an enzyme which in- duces a chemical change, modified by the further action of the soluble ferment. Many of the enzymes carry on their work at a low temperature, as in the curing of meat and cheese in cold storage.^* 32. General Relationship of Chemical, Physical, and Bacteriological Changes. — It cannot be said that the beneficial results derived from the cooking of foods are due to either chemical, physical, or bacteriological change alone, but to the joint action of the three. In order to secure a chemical change, a physical change must often precede, and a bacteriological change can- not take place without causing a change in chemical com- position ; the three are closely related and interdependent. 33. Esthetic Value of Foods. — Foods should be not only of good physical texture and contain the requisite 36 HUMAN FOODS AND THEIR NUTRITIVE VALUE nutrients, but they should also be pleasing to the eye and served in the most attractive manner. Some foods owe a part of their commercial value to color, and when they are lacking in natural color they are not consumed with a relish. There is no objection to the addition of coloring matter to foods, provided it is of a non-injurious character and does not affect the amount of nutrients, and that its presence and the kind of coloring material are made known. Some foods contain objectionable colors which are eliminated during the process of manu- facture, as in the case of sugar and flour. As far as re- moval of coloring matter from foods during refining is concerned, there can be no objection, so long as no inju- rious reagents or chemicals are retained, as the removal of the color in no way affects the nutritive value or permits fraud, but necessitates higher purification and refining. The use of chemicals and reagents in the preparation and refining of foods is considered permissible in all cases where the reagents are removed by subsequent processes. In the food decisions of the United States Department of Agriculture, it is stated : " Not excluded under this pro- vision are substances properly used in the preparation of food products for clarification or refining and elimi- nated in the further process of manufacture." ^^ CHAPTER III VEGETABLE FOODS 34. General Composition. — Vegetable foods, with the exception of cereals, legumes, and nuts, contain a smaller percentage of protein than animal food products. They vary widely in composition and nutritive value ; in some, starch predominates, while in others, sugar, cellulose, and pectin bodies are most abundant. The general term " vegetable foods " is used in this work to include roots, tubers, garden vegetables,, cereals, legumes, and all prepared foods of vegetable origin. 35. Potatoes contain about 75 per cent of water and 25 per cent of dry matter, the larger portion being starch. There is but little nitrogenous material in the potato, only 2.25 per cent, of which about half is in the form of proteids. There are ten parts of non-nitroge- nous substance to every one part of nitrogenous; or, in other words, the potato has a wide nutritive ratio, and as an article of diet needs to be supplemented with foods rich in protein. The mineral matter, cellu- 37 38 HUMAN FOODS AND THEIR NUTRITIVE VALUE lar tissue, and fat in potatoes are small in amount, as are also the organic acids. Mechanically considered, the potato is composed of three parts, — outer skin, inner skin, and flesh. The layer immediately beneath the outer skin is slightly colored, and is designated the fibro-vascu- lar layer. The outer and inner skins combined make up about 10 per cent of the weight of the potato. A large portion of the pro- tein of the potato is albumin, which is soluble in water. When potatoes are peeled, cut in small pieces, and soaked in water for several hours before boiling, 80 per cent of the crude protein, or total nitrogenous material, is extracted, render- ing the product less valuable as food. When potatoes are placed directly in boiling water, the losses of nitroge- nous compounds are reduced to about 7 per cent, and, when the skins are not removed, to i per cent. Di- gestion experiments show that 92 per cent of the starch and 72 per cent of the protein are digested. ^^ Com- pared with other foods, potatoes are often a cheap source of non-nitrogenous nutrients. If used in excessive amounts, however, they have a tendency to make the ration unbalanced and too bulky. Fig. g. — Transverse Section OF Potato. (After Cowden and BUSSARD.) a, skin ; b, cor- tical layer; c, outer medullary layer; li, inner medullary layer. VEGETABLE FOODS Mechanical Composition of the Potato Unpeeled potatoes Outer, or true skin Inner skin, or fibro-vascular layer * Flesli 39 Per Cent lOO.O 2.5 8.5 89.0 Chemical Composition of the Potato Carbohydrates Water Crude Pro- tein Fat Nitro- gen- uee- extract Fiber Ash Outer, or true skin . . 80.1 % 2.7 % 0.8 , % 14. % 6 % 1.8 Inner skin, or fibro- vascular layer . . Flesh 83.2 8I.I 2-3 2.0 O.l O.I 12.6 15-7 0.7 0-3 1. 1 0.8 Average of 86 Ameri- can analyses f . . Average of 118 Euro- 78.0 2.2 0.1 18. 8 0.9 pean analyses % . ■ 75.0 2.1 0.1 21.0 0.7 i.r 36. Sweet Potatoes contain more dry matter than white potatoes, the difference being due mainly to the presence of about 6 per cent of sugar. There is approxi- mately the same starch content, but more fat, protein, * Including a small amount of flesh. t From an unpublished compilation of analyses of American food products. t Konig, " Chemie der Nahrungs- und Genussmittel," 3d ed., II, p. 626. 40 HUMAN FOODS AND THEIR NUTRITIVE VALUE and fiber. As a food, they supply a large amount of non-nitrogenous nutrients. 37. Carrots contain about half as much dry matter as potatoes, and half of the dry matter is sugar, nearly equally divided between sucrose and levulose, or fruit sugar. Like the potato, carrots have some organic acids and a relatively small amount of proteids. In carrots and milk there is practically the same per cent of water. The nutrients in each, however, differ both as to kind and proportion. Experiments with the cooking of carrots show that if a large amount of water is used, 30 per cent or more of the nutri- ents, particularly of the more soluble sugar and albu- min, are extracted and lost in the drain waters. ^^ The color of the carrot is due to the non-nitrogenous com- pound carrotin, CggHgg. Carrots are valuable in a ration not because of the nutrients they supply, but for the palatabihty and the mechanical action which the vegetable fiber exerts upon the process of digestion. 38. Parsnips contain more solid matter than beets or carrots, of which 3 to 4 per cent is starch. The starch grains are very small, being only about one twentieth the size of the potato starch grains. There is 3 per cent of sugar and an appreciable amount of fat, more than in any other of the vegetables of this class, and seven times as much as in the potato. The mineral matter is of somewhat different nature from that in potatoes ; in parsnips one half is potash- and one quarter phosphoric VEGETABLE FOODS 41 acid, while in potatoes three quarters are potash and one fifth phosphoric acid. 39. Cabbage contains very little dry matter, usually less than 10 per cent. It is proportionally richer in nitrogenous com- pounds than many vegetables, as about two of the ten parts of dry matter are crude protein, which makes the nutritive ratio one to five. During cooking 30 to 40 per cent of the nutrients are extracted. Cabbage imparts to the ration bulk but compara- tively little nutritive material. It is a valuable food adjunct, particularly used raw, as in a salad, when it is easily digested and retains all of the nutrients. ^^ 40. Cauliflower has much the same general composi- tion as cabbage, from which it differs mainly in mechan- ical structure. 41. Beets. — The garden beet contains a little more protein than carrots, but otherwise has about the same general composition- and the statements made in regard Fig. 10. -Graphic Composition of Cahumse. 42 HUMAN FOODS AND THEIR NUTRITIVE VALUE to the losses of nutrients in the cooking of carrots and to their use in the dietary apply also to beets. 42. Cucumbers contam about 4 per cent of dry matter. The amount of nutrients is so small as to scarcely allow them to be considered a food. They are, however, a valuable food adjunct, as they impart palata- bility. 43. Lettuce contains about 7 per cent of solids, of which 1.5 is protein and 2.5 starch and sugar. While low in nutrients, it is high in dietetic value, because of the chlorophyll which it contains. It has been suggested that it is valuable, too, for supplying iron in an organic form, as there is iron chemically combined with the chlorophyll. 44. Onions are aromatic bulbs, valuable for condi- meiital rather than nutritive purposes. They contain essential and volatile oils, which impart characteristic odor and flavor. In the onion there are about 1.5 per cent of protein and 9.5 per cent of non-nitrogenous material. Onions are often useful in stimulating the digestive tract to action. 45. Spinach is a valuable food, not to be classed merely as a relish. Its composition is interesting ; for, although there is 90 per cent water, and less than 10 per cent dry matter, it still possesses high food value. Spinach contains 2.1 percent crude protein, or about one part to every four parts of carbohydrates. In potatoes. VEGETABLE FOODS 43 turnips, and beets there are ten or more parts of car- bohydrates to every one part of protein. 46. Asparagus is composed largely of water, about 93 per cent. The dry matter, however, is richer in pro- tein than that of many vegetables. Asparagus contains, too, an amid compound, asparagin, which gives some of the characteristics to the vegetable. 47. Melons. — Melons contain from 8 to lo per cent of dry matter, the larger portion of which is sugar and allied carbohydrates. The flavor is due to small amounts of essential oils and to organic acids associated with the sugars. Melons possess condimental rather than nutritive value. 48. Tomatoes. — The tomato belongs to the night- shade family, and for this reason was long looked upon with suspicion. It was first used for ornamental purposes and was called " love-apple." Gradu- ally, as the idea of its poisonous nature be- came dis- non-sugar solids ^^jj^^^ j^ g-rew more and more Fig. II. -Graphic Composition of popular as a food, until Tomato. . , tt • i r- now m the United States it is one of the most common garden vegetables. It contains 7 per cent of dry matter, 4 per cent of 44 HUMAN FOODS AND THEIR NUTRITIVE VALUE which is sucrose, dextrose, and levulose. It also con- tains some malic acid, and a small amount of pro- teids, amids, cellulose, and coloring material. In the canning of tomatoes, if too much of the juice is excluded, a large part of the nutritive material is lost, as the sugars and albumins are all soluble and readily removed. ^^ If the seeds are objectionable, they may be removed by straining and the juice added to the fleshy portion. The product then has a higher nutritive value than if the juice had been discarded with the seeds. 49. Sweet Corn. — Fresh, soft, green, sweet corn con- tains about 75 per cent of water. The dry matter is half starch and one quarter sugar. The protein content makes up nearly 5 per cent, a larger proportional amount than is found in the ripened corn, due to the fact that the proteids are deposited in the early stages of growth and the carbohydrates mainly in the last stages. Sweet corn is a vegetable of high nutritive value and palata- bility. 50. Eggplant contains a high per cent of water, — 90 per cent. The principal nutrients are starch and sugar, which make up about half the weight of the dry matter. It does not itself supply a large amount of nutrients, but the way in which it is prepared, by combination with butter, bread crumbs, and eggs, makes it a nutritious and palatable dish, the food value being derived mainly from the materials with which it is combined, the eggplant giving the flavor and palatability. VEGETABLE FOODS 45 51. Squash and Pumpkin. — Squash has much the same general composition and food vakie as beets and carrots, although it belongs to a different family. Pump- kins contain less dry matter than Squa-sh. The dry mat- ter of both is composed largely of starch and sugar and, like many other of the vegetables, they are often com- bined with food materials containing a large amount of nutrients, as in pumpkin and squash pies, where the food value is derived mainly from the milk, sugar, eggs, flour, and butter or other shortening used. 52. Celery. — The dry matter of celery is compar- atively rich in nitrogenous material, although the amount is small, and the larger proportion is in non- proteid form. When grown on rich soil, celery may contain an appreciable quantity of nitrates and nitrites, which have not been converted into amids and proteids. The supposed medicinal value is probably due to the nitrites which are generally present. Celery is valuable from a dietetic rather than a^'nutritive point of view. 53. Sanitary Condition of Vegetables. — The conditions under which vegetables are grown have much to do with their value, particularly from a sanitary point of view. Uncooked vegetables often cause the spread of diseases, particularly those, as cholera and typhoid, affecting the digestive tract. Particles of dirt containing the disease- producing organisms adhere to the uncooked vegetable and find their way into the digestive tract, where the bac- teria undergo incubation. When sewage has been used 46 HUMAN FOODS AND THEIR NUTRITIVE VALUE for fertilizing the land, as in sewage irrigation, the vege- tables are unsound from a sanitary point of view. Such vegetables should be thoroughly cleaned and also well cooked, in order to render them sterile. Vegetables to be eaten in the raw state should be dipped momentarily into boihng water, to destroy the activity of the germs present upon the surface. They may then be immedi- ately immersed in ice-cold water, to preserve the crisp- ness. 54. Miscellaneous Compounds in Vegetables. — In ad- dition to the general nutrients which have been discussed, many of the vegetables contain some tannin, glucosides, and essential oils ; and occasionally those grown upon rich soils have appreciable amounts of nitrogen com- pounds, as nitrates and nitrites, which have not been built up into proteids. Vegetables have a unique value in the dietary, and while as a class they contain small amounts of nutrients, they are indispensable for promot- ing health and securing normal digestion of the food. 55. Canned Vegetables. — When sound vegetables are thoroughly cooked to destroy ferments, and then sealed in cans while hot, they can be kept for a long time without any material impairment of nutritive value. During the cooking process there is lost a part of the essential oils, which gives a slightly different flavor to the canned or tinned goods. ^'' In some canned vege- tables preservatives are used, but the enactment and enforcement of national and state laws have greatly VEGETABLE FOODS 47 reduced their use. When the cans are made of a poor quahty of tin, or the vegetables are of high acidity, some of the metal is dissolved in sufficient quantity to be objectionable from a sanitary point of view.^^ 56. Edible Portion and Refuse of Vegetables. — Many vegetables have appreciable amounts of refuse,-'^ or non-edible parts, as skin, pods, seeds, and pulp, and in determining the nutritive value, these must be consid- ered, as in some cases less than 50 per cent of the weight of the material is edible portion, which propor- tionally increases the cost of the nutrients. Ordinarily, the edible part is richer in protein than the entire material as purchased. In some cases, however, the refuse is richer in protein, but the protein is in a less available form. See comparison of potatoes and potato skins. CHAPTER IV FRUITS; FLAVORS, AND EXTRACTS 57. General Composition. — Fruits are characterized by containing a large amount of water and only a small amount of dry matter, which is composed mainly of sugar and non-nitrogenous compounds. Fruits contain but little fatty material and protein. A large portion of the total nitrogen is in the form of amid compounds. Organic acids, as citric, tartaric, and malic, are found in all fruits, and the essential oils form a characteristic feature. The taste of fruits is due mainly to the blend- ing of the various organic acids, essential oils, and sugars. Although fruits contain a high per cent of water, they are nevertheless valuable as food.-- The constituents present to the greatest extent are sugars and acids. The sugar is not all like the common granu- lated sugar, but in ripe fruits a part is in the form known as levulose or fruit sugar, which is two and a half times sweeter than granulated sugar. Sugars are valuable for heat- and fat-producing purposes, but not for muscle repairing. Proteids are the muscle-forming nutrients. The organic acids, as malic acid in apples, citric acid in lemons and oranges, and tartaric acid in grapes, have characteristic medicinal properties. The FRUITS, FLAVORS, AND EXTRACTS 49 sugar, proteid, and acid content of some of our more common fruits is given in the following table i^^ Composition ov Fruits Water Proteids Sl'C.AR Acid in Juice Kind of Acid Per Cent Per Cent Per Cent Per Cent Apples (Baldwin) 85.0 0.50 10.75 0.92 Malic Apples, sweet . . 86.0 0.50 11.75 0.20 Malic Blackberries . . 88.9 0.90 11.50 0,75 Malic Currants . . 86.0 — 1.96 5.80 Tartaric Grapes . 83.0 1.50 10 to 16 1.2 to 5 Tartaric Strawberries 90.8 0.95 5.36 1.40 Malic Oranges . . 85.0 1. 10 1000 1.30 Citric Lemons 84.0 0.95 2.00 7.20 Citric In addition to sugars, acids, and proteids, there are a great many other compounds in fruits. Those which give the characteristic taste are called essential or vola- tile oils. 58. Food Value. — When the nutrients alone are con- sidered, fruits appear to have a low food value, but they should not be judged entirely on this basis, because they impart palatability and flavor to other foods and exercise a favorable influence upon the digestive process. In the human ration fruits are a necessary adjunct. 59. Apples. — Apples vary in composition with the variety and physical characteristics of the fruit. In general they contain from 10 to 16 per cent of dry mat- ter, of which 75 per cent, or more, is sugar or allied E 50 IIU.MAN FOODS AND THEIR NUTRITIVE \-ALUE Fig. 12. -Gkvphic Composition OF Apple. tial oils. During storage so further ripening, resultin sucrose, and there is a sHght loss of weight, due to the formation of carbon dioxid. The apple is an important and valuable adjunct to the dietary.^ 60. Oranges contain nearly the same pro- portion of dry matter as apples, the larger part of which is sugar. Citric acid predomi- carbohydrates. Among the organic acids malic pre- dominates, and the acidity ranges from o. i to 0.8 per cent. Apples contain but little protein, less than i per cent. There is some pectin, or jelly-like sub- stance closely related to the carbohydrates. The flavor of the apple varies with the content of sugar, organic acids, and essen- me apples appear to undergo in partial inversion of the Fig. 13. — Graphic Composition of Orange, FRUITS, FLAVORS, AXl) EXTRACTS 51 nates and ranges in different varieties from i to 2.5 per cent. The amounts of protein, fat, and cellulose are small. In some varieties of oranges there is more iron and sulphur than is usually found in fruits. All fruits, however, contain small amounts, but not as much as is found in green vegetables. The average composition of oranges is as follows : Physical Composition' Rind Pulp Juice Per Cent 20 to 30 ^5 to 35 35 to 50 Chemical CoMPOSinoN OF Edible Portion Per Cent Solids ID to 16 Sugars 8 to 1 2 Citric acid i to 2.5 Asli 0.5 61. Lemons differ from oranges in containing more citric acid and less sucrose, levulose, and dextrose. The ash of the lemon is somewhat similar in general compo- sition to the ash of the orange, but is larger in amount. The average composition of the lemon is as follows : Physical Composition Rind Pulp Juice Per Cent 25 to 35 25 to 35 40 to 55 Chemical Composition of Edible Portion Solids Sugar Citric acid Per Cent 10 to 12 2 to 4 6 to 9 62. Grape Fruit. — The rind and seed of this fruit make up about 25 per cent, leaving 75 per cent as edible portion. The juice contains 14 per cent solids, of 52 HUMAN FOODS AND THEIR NUTRITIVE VALUE which nearly lo per cent is sugar and 2.5 per cent is citric acid. There is more acid in grape fruit than in oranges and appreciably less than in lemons. The characteristic flavor is due to a glucoside-like material. Otherwise the composition and food value are about the same as of oranges. 63. Strawberries contain from 8 to 12 per cent of dry matter, mainly sugar and malic acid. The pro- tein, fat, and ash, usually make up less than 2. per cent. Essential oils and coloring substances are present in small amounts. It has been estimated that it would require 75 pounds of strawberries to supply the protein for a daily ra- tion. Nevertheless they are valuable in the die- tary. It has been sug- gested that the malic and other acids have antisep- tic properties which, add- ed to the appearance and palatability, make them a desirable food adjunct. Strawberries have iiigh dietetic rather than high food value. Fig. 14. — Graphic Composition OF Stkawiierrv. FRUITS, FLAVORS, AND EXTRACTS ^3 64. Grapes contain more dry matter than apples or oranges. There is no appreciable amount of protein or fat, and while they add some nutrients, as sugar, to the ration, they do not contribute any quantity. Their value, as in the case of other fruits, is due to palatability and indirect effect upon the digestibility of other foods. In the juice of grapes there is from lo to 15 per cent or more of sugar, as sucrose, levulose, and dextrose. Grapes contain also from i to 1.5 per cent of tartaric acid, which, during the process of manufacture into wine, is rendered insoluble by the alcohol formed, and the product, known as argole, is used in the preparation of cream of tartar. Differences in flavor and taste of grapes are due to variations in the sugar, acid, and essential oil content. 65. Peaches contain about 12 per cent of dry matter, of which over ro per cent is sugar and other carbohy- drates. There is less than 1.5 percent of protein, fat, and mineral matter and about 0.5 per cent of acid. The peach contains also a very small amount of hydrocyanic acid, which is more liberally present in the kernel than in the fruit. Flavor is imparted mainly by the sugar and essential oils. Peaches vary in composition with variety and environment.^^ 66. Plums contain the most dry matter of any of the fruits, about 22 per cent, mainly sugar. About one per cent is acid and about 0.5 per cent are protein and ash. There are a great many varieties of plums, vary- 54 HUMAN FOODS AND THEIR NUTRITIVE VALUE ing in composition. Dried plums (prunes) have mildly laxative properties. 67. Olives. — The ripe olive contains about 15 per cent of oil, exclusive of the pit, which makes up 20 per cent of the weight. In green, preserved olives there is considerably less oil. Because of the oil the olive has food value. Olive oil is slightly laxative and assists mechanically in the digestion of foods. 68. Figs. — Dried figs contain about 50 per cent of sugar and 3.5 per cent of protein. The fig has a mildly laxative action. 69. Dried Fruits. — Many fruits are prepared for market by drying. The dried fruit has a slightly different composition from the fresh fruit because of loss of the volatile and essential oils, and minor chemical changes which take place during the drying process. When free from preservatives, dried fruits are valuable adjuncts to the dietary and can be advantageously used when fresh fruits are not obtainable. 70. Canning and Preservation of Fruits. — To obtain the best results in canning, the fruit should not be over- ripe. After the ripened state has been reached fermen- tation and bacterial changes occur, and it is more difficult to preserve the fruit than when not so fully matured.^* When a fruit has begun to ferment, it is hard to destroy the ferment bodies and their spores so as to prevent further ferment action. The chemical changes that oc- FRUITS, FLAVORS, AND EXTRACTS 55 cur ill the last stages of ripening are similar to those which take place during the cooking process whereby the pectin or jelly-like substances are rendered more soluble and digestible. 71. Adulterated Canned Fruits. — Analyses of a num- ber of canned fruits, made by various Boards of Health, show the presence of small amounts of arsenic, tin, lead, and other poisonous metals. The quantity dis- solved depends upon the kind, age, and condition of the canned goods and the state of the fruit when canned. The longer a can of fruit or vegetable has been kept in stock, the larger is the amount of tin or metal that has been dissolved. When fresh canned, there is usually very little dissolved tin, but in old goods the amount may be comparatively large. The tin used for the can is occasionally of poor quality and may contain some arsenic, which also is dissolved. The occasional use of canned goods preserved in tin is not objectionable, but they should not be used continually if it can be avoided. Preservatives, as borax, salicylic acid, benzoic acid, and sodium sulphate, are sometimes added to prevent fer- mentation and to preserve the natural appearance of the fruit or vegetable. ^^ 72. Fruit Flavors and Extracts. — Formerly all fruit extracts and flavors were obtained from vegetable sources ; at present many are made in the chemical laboratory by synthetic methods ; that is, by combining simpler organic compounds and radicals to produce the 56 HUMAN FOODS AND THEIR NUTRITIVE VALUE material having the desired flavor and odor. The vari- ous fruit flavors are definite chemical compounds, and can be produced in the laboratory as well as in the cells of plants. When properly made, there is no difference in chemical composition between the two. As prepared in the laboratory, however, traces of acids, alkalies, and other compounds, used in bringing about the necessary chemical combination, are often present, not having been perfectly removed. Hence it is that natural and artifi- cial flavors differ mainly in the impurities which the artificial flavors may contain. Some of the flavoring materials have characteristic medicinal properties, as the flavor of bitter almond, which contains hydrocyanic acid, a poisonous substance. Flavors and extracts should not be indiscriminately used. In small amounts they often exert a favorable influence upon the digestion of foods, and the value of some fruits is in a large measure due to the special flavors they con- tain. A study of the separate compounds which impart flavor to fruits, as the various aldehydes, ethers, and or- ganic salts, belongs to organic chemistry rather than to foods. Some of the simpler compounds of which flavors are composed may exist in entirely different form or combination in food products ; as for example, pineapple flavoring is ethyl butrate. This can be prepared by combination of butyric acid from stale butter with alcohol which supplies the ethyl radical. The chemical union of the two produces the new compound, ethyl butrate, the distinctive flavoring substance of the pineapple. FRUITS, FLAVORS, AND EXTRACTS 57 Banana flavor can be made from stale butter, caustic soda, and chloroform. None of these materials, as such, go into the flavor, but an essential radical is taken from each. These manufactured products, when properly made, are in every essential similar to the flavor made by the plant and stored up in the fruit. The plant combines the ma- terial in the laboratory of the plant cell, and the manu- facturer of essences puts together these same constitu- ents in a chemical laboratory. In the fruit, however, the essential oil is associated with a number of other compounds. CHAPTER V SUGARS, MOLASSES, SYRUP, HONEY, AND CONFECTIONS 73. Composition of Sugars. — The term "sugar" is applied to a large class of compounds composed of the elements carbon, hydrogen, and oxygen. Sugars used for household purposes are derived mainly from the sugar cane and the sugar beet.^^ At the present time about two fifths are obtained from the cane and about three fifths from the beet. When subjected to the same degree of refining, there is no difference in the chemical composition of the sugars from the two sources; they are alike in every respect and the chem- ist is unable to determine their origin. The production of sugar is an agricultural industry; the methods of manufacture pertain more to industrial chemistry than to the chemistry of foods, and therefore a discussion of them is omitted in this work.-'' 74. Commercial Grades of Sugar. — Sugars are graded according to the size of the granule, the color and general appearance of the crystals, and the per cent of sucrose or pure sugar. Common granulated sugar is from 98.5 to 99.7 per cent pure sucrose. The impuri- 5S %%m Fig. 15. — Sugar Cr\stals. SUGARS, MOLASSES, SYRUP, HONEY, CONFECTIONS 59 ties consist mainly of moisture and mineral matter. In the process of refining, sulphur fumes are frequently used for bleaching and clarifying the solution.^" The sulphurous acid formed is neutralized with lime, which is rendered insol- uble and practically all removed in subsequent filtrations. There are, however, traces of sul- phates and sulphites in ordinary sugar, but these are in such small amounts as not to be injurious to health. When sugar is burned, as in the bomb calorimeter, so as to permit collection of all of the products of combustion, granulated sugar yields about 0.0 1 of a per cent of sulphur dioxid.'^ Occa- sionally coloring substances, as a small amount of in- digo, are added to yellow tinged sugars to impart a white color, much on the same principle as the bluing of clothes. The amount used is usually ex- tremely small, and the effect on health has never been determined. Occasionally, however, bluing is used to such an extent that a blue scum appears when the sugar is boiled with water. Sugar has high value for the production of heat and energy. Diges- tion experiments show that when it is used in the die- tary in not excessive amounts, it is directly absorbed by 6o HUMAN FOODS AND THEIR NUTRITIVE VALUE the body and practically all available. It can advan- tageously be combined with other foods to form a part of the ration.^'' When a ration contains the requisite amount of protein, sugar is used to the best advantage. Alone it is incapable of sustaining life, because it does not contain any nitrogen. When sugar was substituted for an excess of protein in a ration, it was found to pro- duce heat and energy at much less expense. Many foods, as apples, grapes, and small fruits, contain appre- ciable amounts of sugar and owe their food value al- most entirely to their sugar content. In the dietary, sugar is too frequently regarded as a condiment instead of a nutrient, to be used for imparting palatability rather than for purposes of nutrition. While valuable for improving the taste of foods, the main worth of sugar is as a nutritive substance; used in the prepara- tion of foods it adds to the total heat and energy of the ration. Sugar is sometimes used in excessive amounts and, as is the case with any food or nutrient, when that occurs, nutrition disturbances result, due to misuse of the food. Statistics show that the average consump- tion of sugar in the United States is nearly 70 pounds a year per capita. In the dietary of the adult, sugar to the extent of four ounces per day can be consumed advantageously. The exclusion of sugar from the diet of children is a great mistake, as they need it for heat and energy and to conserve the protein for growth. " Sugar is one of the most important form.s in which carbo- hydrates can be added to the diet of children. The great reducliju SUGARS, MOLASSES, SYRUP, HONEY, CONFECTIONS 6l in the price of sugar wiiich has taken place in recent years is probably one of the causes of the improved physique of the rising generation. The fear that sugar may injure children's teeth is largely illusory. The negroes who live largely on sugar cane have the finest teeth the world can show. If injudiciously taken, sugar may, however, injure the child's appetite and digestion. The crav- ing for sweets which children show is no doubt the natural expres- sion of a physiological need, but they should be taken with, and not between, meals." ^^ 75. Sugar ia the Dietary. — Sugar has an important place in the dietary. It not only serves for the produc- Protet'n. Fd.t Cafbokydrdtes Fig. i6. — Nutrients of a Ration with Sugar. tion of heat and energy in the body, but is also valuable in enabling the proteids to be used more economically. In reasonable amounts, it is particularly valuable in the dietary of growing children, as the proteids of the food are then utilized to better advantage for growth. The unique value of sugar depends upon its inteUigent use and its proper combination with other foods, particularly with those rich in the nitrogenous compounds or pro- teids. Sugar alone is incapable of sustaining Hfe, but combined with other foods is a valuable nutrient. The amount which can be advantageously used depends 62 HUMAN FOODS AND THEIR NUTRITIVE VALUE largely upon the individual. Ordinarily three to five ounces per day is sufficient, although some persons can- not safely consume as much as this. In the case of diabetes mellitus, the amount of sugar in the ration must be materially reduced. Persons in normal health and engaged in outdoor work can use sugar to advan- tage.^^ Many of the "harvest drinks," made largely from molasses with a little ginger, and used extensively in some localities, are not without merit, as they contain "protcc'n ^ F^t ^. Oa rboky (Urates Fig. 17, — Ni'TRiENTS Cooked. Skins, Wet ani> Dry. to the action of the digestive fluids. Experiments show that 42 per cent of the protein of baked skinned beans is soluble in pepsin and pancreatin solutions, while under similar conditions there is only 3.85 per cent of the protein soluble from beans baked without removal of the skins. 87. Use of Beans in the Distary. — There is no veg- etable food capable of furnishing so much protein at 74 HUMAN FOODS AND THEIR NUTRITIVE VALUE such low cost as beans; from a pound costing five cents about one fifth of a pound of protein and three fifths of a pound of carbohydrates are obtained. Beans can, to a great extent, take the place of meats in the dietary. There is more protein in beans than in beef. Four ounces of uncooked beans or six ounces of baked beans are as much as can conveniently be combined in the dietary, and these will furnish a quarter of the protein of the ration. In the case of active out-of-door laborers over a pound of baked beans per day is often consumed with impunity. 88. String Beans. — String beans — green beans with pod — contain a large amount of water, 85 to 88 per cent. The dry matter is rich in protein, nearly 20 per cent, although in the green beans as eaten, containing 85 per cent water, there is less than 2.^ per cent. Lima beans are richer in protein than string beans, as the green pod is not included. String beans are valuable both for the nutrients they contain and for the favorable influence they exert upon the digestibility of other foods. 89. Peas. — In general composition and digestibility, peas are quite similar to beans. They belong to the same family, Leguminosas, and the protein of each is similar in quantity and general properties. The state- ments made in regard to the composition, digestibility, and use of beans in the dietary apply with minor modi- fications to peas. When used in the preparation of soups, they add appreciable amounts of nutrients. LEGUMES AND NUTS 75 Fig. 21. — Pea Starch Granules. 90. Canned Peas. — In order to impart a rich green color, copper sulphate has been used in the canning of peas. Physiologists differ as to its effect upon health. While a little may not be particularly injurious, much interferes with normal digestion of the food and forms insoluble copper proteids. In some countries a small 76 HUMAN FOODS AND THEIR NUTRITIVE VALUE amount of copper sulphate is tolerated, while in others it is prohibited. 91. Peanuts. — Peanuts differ from peas and beans in containing more fat. They should be considered a food, for at ordinary prices they furnish a large amount of protein and fat. Like the other members of the legume family, the peanut is rather slow of digestion and requires considerable intestinal work for completion of the process. NUTS 92. General Composition. — Nuts should be regarded as food, for they contribute to a ration appreciable amounts of nutrients. The edible portion of nearly all is rich in fat ; pecans, for example, contain as high as 70 per cent. In protein content nuts range from 3 per cent in cocoanuts to 30 per cent in peanuts. The car- bohydrate content is usually comparatively low, less than 5 per cent in hickory nuts, although there is nearly 40 per cent in chestnuts. On account of high fat content, nuts supply a large amount of heat and energy.^^ 93. Chestnuts are characterized by containing less fat and protein and much more carbohydrate material, espe- cially starch, than is found in other nuts. In southern Europe chestnuts are widely used as food ; the skins are removed, and the nuts are steamed, boiled, or roasted, and sometimes they are dried and ground into flour. Chestnuts are less concentrated in protein and fat, and LEGUMES AND NUTS 77 form a better balanced food used alone than do other nuts. 94. The Hickory Nut, which is a characteristically American nut, contains in the edible portion about 1 5 per cent protein, 65 per cent fat, and 12 per cent car- bohydrates. 95. The Almonds used in the United States come chiefly from southern Europe, although they are suc- cessfully raised in California. They contain about 55 per cent fat and 22 per cent protein. The flavor of almonds is due to a small amount of hydrocyanic acid. 96. Pistachio. — Some nuts are used for imparting color and flavor to food products, as the pistachio nut, the kernel of which is greenish in color and imparts a flavor suggestive of almonds. The pistachio has high food value, as it is rich in both fat and protein. It is employed in the manufacture of confectionery and in ice cream for imparting flavor and color. 97. Cocoanuts grow luxuriantly in many tropical coun- tries, and have a high food value. They are character- istically rich in fat, one half of the edible portion being composed of this nutrient. For tropical countries they supply the fat of a ration at less expense than any other food. When used in large amounts they should be sup- plemented with foods rich in carbohydrates, as rice, and in proteids, as beans. Cocoanut milk is proportionaHy richer in carbohydrates and poorer in fat and protein 78 HUMAN FOODS AND THEIR NUTRITIVE VALUE than the meat of the cocoanut. In discussing the co- coanut, Woods states : ^* " Tlie small, green, and immature nuts are grated fine for medici- nal use, and when mixed with the oil of the ripe nut it be- comes a healing ointment. The jelly which lines the shell of the more mature nut furnishes a delicate and nutritious food. The milk in its center, when iced, is a most delicious luxury. Grated cocoanut forms a part of the world-renowned East India condiment, curry. Dried, shredded (desiccated) cocoanut is an important article of commerce. From the oil a butter is made, of a clear, whitish color, so ricli in fat, that of water and foreign substances combined there are but 0.0068. It is better adapted for coolcing than for table use. At present it is chiefly used in hospitals, but it is rapidly finding its way to the tables of the poor, particularly as a substitute for oleomargarine." 98. Use of Nuts in the Dietary. — When nuts can be secured at a low price per pound, ten cents or less, they compare favorably in nutritive value with other staple foods. Digestion experiments with rations composed largely of nuts show that they are quite thoroughly digested. Professor Jaffa of the California Experiment Station, in discussing the nutritive value of nuts and fruits, says : ^ '• It is certainly an error to consider nuts merely as an accessory to an already heavy meal, and to regard fruit merely as something of value for its pleasant flavor, or for its hvgienic or medicinal virtues. The agreement of one food or another with any person is more or less a personal idiosyncrasy, but it seems fair to say that those with whom nuts and fruits agree, can, if they desire, readily secure a con- siderable part of their nutritive material from such sources.'' LEGUMES AND NUTS Average Composition of Nuts (From Fifteenth Annual Report, Maine Agricultural Experiment Station.) 79 Refuse Edible Portion Edible Portion Water Prot. Fat Carb. Ash Value* PER Lb. % % % % % % % Calories Almonds 64.8 35-2 1-7 7-3 19-3 6.2 0.7 1065 Almonds, kernels — lOO.O 4.8 21.0 54-9 17-3 2.0 3030 Brazil nuts . . . 49.6 504 2.7 8.633.6 3-5 2.0 1545 Filberts . . . 52.1 47-9 1.8 7-5 31-3 6.2 I.I 1575 Filberts, kernels — 100,0 3-7 15.6 65-3 13.0 2.4 3290 Hickory nuts . 62.2 37.8 1.4 5.8 25.5 4-3 0.8 1265 Pecans .... 497 5° 3 1.4 5.2 35-6 7.2 08 1733 Pecans, kernels — 1 00.0 2.9 10.3 70.8 14-3 17 3445 Walnuts . . 58.0 42.0 1.2 7.0 27.0 6.1 07 1385 Walnuts, kernels — 100 2.8 16.7 644 14.8 1-3 3305 Chestnuts . . 16.I 83-9 31.0 5-7 6.7 39'0 1-5 1115 Acorns . . . 356 64.4 2.6 5.2 24.1 3P-9 1.6 1690 Beechnuts . . 408 59.2 2-3 130 34.0 7.8 2.1 1820 Butternuts . . 86.4 13-6 0.6 3-8 8-3 0.5 04 43° Litchi nuts . . 41.6 58.4 10.5 1-7 0.1 45.2 0.9 875 Pinon, P. ednlis 40.6 59-4 2 8.7 36.8 10.2 17 1905 Piiion, P. moiiophylla 41.7 58.3 2.2 3-8 35 4 '5-3 1.6 1850 Piiion, P. sabiniana . 77.0 23.0 1.2 6.5 12.3 1.9 I.I 675 Pistachio, kernels 1 00.0 4.2 22.6 54-5 15.6 31 3010 Peanuts, raw . . . 26.4 736 6.9 20.6 307 13.8 1.6 193s Peanuts, kernels . . — lOO.O 93 27.9 42.0 18.7 2.1 2640 Roasted peanuts 32.6 67.4 I.I 20.6 33-1 10.9 17 1985 Shelled peanuts . . — TOO 1.6 30-5 49.2 16.2 2-5 2955 Peanut butter . . . — — 2.0 293 46.6 17.1 t5.o 2830 Cocoanuts .... 48.8 51.2 7.2 2.9 25.9 14-3 09 1415 Cocoanuts, shredded — — 3-5 63 57-3 31.6 1-3 3125 Cocoanut milk . . — — 927 0.4 1-5 4.6 0.8 97 * Calculated from analyses. t Including salt, 4.1. CHAPTER VII MILK AND DAIRY PRODUCTS 99. Importance in the Dietary. — There is no article of food which enters so extensively into the dietary as milk, and it is one of the few foods which supply all the nutrients, — fats, carbohydrates, and proteids.^^ Milk alone is capable of sustaining life for comparatively long periods, and it is the chief article of food during many diseases. An exclusive milk diet for a healthy adult, however, would be unsatisfactory ; in the case of young children, milk is essential, because the digestive tract has not become functionally developed for the digestion of other foods. It is necessary to consider not only the composition and nutritive value of milk, but also its purity or sanitary condition. 100. General Composition. — Average milk contains about 87 per cent water and 13 per cent dry matter. The dry matter is composed approximately of : Per Cent Fat . . . 3.5 Casein . . . 3.25 Albumin 0.50 Milk sugar . . 0.50 Ash .... 0.75 80 MILK AND DAIRY PRODUCTS 8l Fat is the most variable constituent of milk. Occa- sionally it is found as low as 2 per cent and as high as 6 per cent or more. The poorest and richest milks differ mainly in fat content, as the sugar, ash, casein, Fig. 22. — Milk Fat Globules. and albumin, or " solids of the milk serum," are fairly constant in amount and composition. Variations in the content of fat are due to differences in feed and in the breed and individuality of the animal. 101. Digestibility. — Milk is one of the most com- pletely digested of foods, about 95 per cent of the pro- 82 HUMAN FOODS AND THEIR NUTRITIVE VALUE tein and fat and 97 per cent of the carbohydrates being absorbed and utiUzed by the body. In a mixed ration, the nutrients of milk are practi- cally all absorbed. Milk also exerts a favorable influ- ence upon the digestibility of other foods with which it is combined. This is doubtless due to the digestive action of the special ferments or enzymes which milk contains. In milk there is a soluble ferment material or enzyme which has the power of peptonizing proteids. It is this ferment which carries on the ripening process when cheese is cured in cold storage, and it is believed to be this body which promotes digestion of other foods with which milk is combined.^' Milk is not easily digested by some persons. The tendency to costiveness caused by a milk diet can be largely overcome by the use of salt with the milk, or of some solid food, as toast or crackers, to prevent coagu- lation and the formation of masses resistant to the di- gestive fluids. Barley water and lime water in small amounts are also useful for assisting mechanically in the digestion of milk. Milk at ordinary prices is one of the cheapest foods that can be used. 102. Sanitary Condition of Milk. — Equally as im- portant as composition is the sanitary condition or wholesomeness of milk. Milk is a food material which readily undergoes fermentation and is a medium for the distribution of germ diseases. The conditions under which it is produced and the way in which it is han- MILK AND DAIRY PRODUCTS 83 died determine largely its sanitary value, and are of so much importance in relation to public health that during recent years city and state boards of health have intro- FiG. 23. — Dirt in a Sample of Unsanitary Milk. duced sanitary inspection and examination of milk along with the chemical tests for detecting its adulteration. Some of the more frequent causes of contaminated and unsound milk are: unhealthy animals, poor food and 84 HUMAN FOODS AND THEIR NUTRITIVE VALUE water, unsanitary surroundings of the animals, and lack of cleanliness and care in the handling and transporting of the milk. Outbreaks of typhoid and scarlet fevers and other germ diseases have frequently been traced to a contaminated milk supply.^'' 103. Certified Milk. — When milk is produced under the most sanitary conditions, the number of bacterial bodies per cubic centimeter is materially reduced. In order to supply high grade milk containing but few bac- teria, special precautions are taken in the care of the animals, and in the feeding and milking, and all sources of contamination of the milk are eliminated as far as pos- sible. Such milk, when sold in sterilized bottles', is commonly called "certified milk," indicating that its purity is guaranteed by the producer and that the num- ber of bacteria per unit does not exceed a certain stand- ard, as 8000 per cubic centimeter. Ordinary market milk contains upwards of 50, 000. 104. Pasteurized Milk. — In order to destroy the activity of the bacterial organisms, milk is subjected to a temperature of 157° F. for ten minutes or longer, which process is known as pasteurization. When milk is heated to a temperature above 180°, it is sterilized. Below 157°, the albumin is not coagulated. By pasteur- izing, milk is much improved from a sanitary point of view, and whenever the milk supply is of unknown purity, it should be pasteurized.^^ After the milk has been thus treated, the same care should be exercised in MILK AND DAIRY PRODUCTS 85 liSF r Fig. 24. — Pasteurizing Milk. keeping it protected to prevent fresh inoculation or con- tamination, as though it were unpasteurized milk. For family use milk can be pas- teurized in small amounts in the following way : Before receiving the milk, the re- ceptacle should be thor- oughly cleaned and sterilized with boiling water or dry heat, as in an oven. The milk is loose])'- covered and placed in a pan of water, a false bottom being in the pan so as to prevent unequal heating. The water surrounding the milk is gradually heated until a temperature of 159° F. is registered, and the milk is kept at this temperature for about ten minutes. It is then cooled and placed in the refrigerator. 105. Tyrotoxicon. — ■ Tyrotoxicon is a chemical com- pound produced by a ferment body which finds its way into milk when kept in unsanitary surroundings. It induces digestion disorders similar to cholera, and when present in large amounts, may prove fatal. It some- times develops in cream, ice cream, or cheese, but only when they have been kept in unclean places or pro- duced from infected milk. 601. Color of Milk is often taken as a guide to its purity and richness in fat. While a yellow tinge is 86 HUMAN FOODS AND THEIR NUTRITIVE VALUE usually characteristic of milks rich in fat, it is not a hard and fast rule, for frequently hght-colored milks are richer in fat than yellow-tinged ones. The coloring material is independent of the percentage of fat, and it is not always safe to judge the richness of milk on the basis of color. 107. Souring of Milk. — Souring of milk is due to the action of the lactic acid organism, which finds its way into the milk through particles of dust carried in the air or from unclean receptacles which contain the spores of the organism. ^^ When milk sours, a small amount of sugar is changed to lactic acid which reacts upon the casein, converting it from a soluble to an insoluble con- dition. When milk is exposed to the air at a temperature of from 70° to 90° F., lactic acid fermentation readily takes place. At a low temperature the process is checked, and at a high temperature the organisms and spores are destroyed. In addition to lactic acid ferments, there are large numbers of others which develop in milk, chang- ing the different compounds of which milk is composed. In the processes of butter and cheese making, these fermentation changes are controlled so as to develop the flavor and secure the best grades of butter and cheese. 108. Use of Preservatives in Milk. — In order to check fermentation, boric acid, formalin, and other pre- servatives have been proposed. Physiologists object to their use because the quantity required to prevent fer- MILK AND DAIRY PRODUCTS 87 mentation is often sufficient to have a medicinal effect. The tendency is to use excessive amounts, which may interfere with normal digestion of the food. Milk that is cared for under the most sanitary conditions has a higher dietetic value and is much to be preferred to that which has been kept sweet by the use of preservatives. 109. Condensed Milk is prepared by evaporating milk in vacuum pans until it is reduced about one fourth in bulk, when it is sealed in cans, and it will then keep sweet for a long time. Occasionally some cane sugar is added to the evaporated product. When diluted, evaporated milk has much the same composition as whole milk. When a can of condensed milk has been opened, the same care should be exercised to prevent fermentation as if it were fresh milk. 110. Skim Milk differs in composition from whole milk in fat content. When the fat is removed by the separator, there is often left less than one tenth of a per cent. Skim milk has a much higher nutritive value than is generally conceded, and wherever it can be pro- cured at a reasonable price it should be used in the dietary as a source of protein. 111. Cream ranges in fat content from 15 to 35 per cent. It is generally preferred to whole milk, although it is not as well balanced a food, because it is deficient in protein. Cream should contain at least 25 per cent of fat. 88 HUMAN FOODS AND THEIR NUTRITIVE VALUE 112. Buttermilk is the product left after removal of the fat from cream by churning. It has about the same amount of nutrients as skim milk. The casein is in a slightly modified form due to the development of lactic acid during the ripening of the cream, and on this account buttermilk is more easily digested and assimi- lated by many individuals than milk in other forms. The development of the acid generally reduces the number of species of other than the lactic organisms, and these are increased. 113. Goat's Milk is somewhat richer in sohds than cow's milk, containing about one per cent more proteids, a little more fat, and less sugar. When used as a sub- stitute for human or cow's milk, it generally needs to be slightly diluted, depending, however, upon the composi- tion, of the individual sample. 114. Koumiss is a fermented beverage made from milk by the use of yeast to secure alcoholic fermenta- tion. Koumiss contains about one per cent each of lactic acid and alcohol, and the casein and other nutri- ents are somewhat modified by the fermentation changes. Koumiss is generally considered a non-alcoholic beverage possessing both food and dietetic value. 115. Prepared Milks. — Various preparations are made to resemble milk in general composition. These are mechanical mixtures of sugar, fats, and proteids. Milk sugar, casein, or malted proteids are generally the MILK AND DAIRY PRODUCTS 89 materials employed in their preparation. Often the dried and pulverized solids of skim milk are used. Many of the prepared milks are deficient in fat. While they are not equal to cow's milk, their use is often made necessary from force of circumstances. 116. Human Milk is not as rich in solid matter as cow's milk. It contains about the same amount of fat, one per cent more sugar, and one per cent less proteids. In human milk nearly one half of the protein is in the form of albumins, while in cow's milk there is about one fifth in this form. The fat globules are much smaller than those of cow's milk. In infant feeding it is often necessary to modify cow's milk by the addition of water, cream, and milk sugar, so as to make it more nearly resemble in composition human milk. 117. Adulteration of Milk. — Milk is not as exten- sively adulterated as it was before the passage and en- forcement of the numerous state and municipal laws regulating its inspection and sale. The most frequent forms of adulteration are addition of water and removal of cream. "These are readily detected from the specific gravity and fat content of the milk. The specific gravity of milk is determined by means of the lactom- eter, an instrument which sinks to a definite point in pure milk. In watered milk it sinks to greater depth, depending upon the amount of water added. The fat content of milk is readily and accurately determined by the Babcock test, in which the fat is separated by cen- Fig. 25. — Apparatus usiiD in Testing Milk. I, pipette ; 2, lactometer : j, acid measure ; 4, centrifuge ; 5, test bottle. 90 MILK AND DAIRY PRODUCTS 9I trifugal action. For the detection of adulterated milk the student is referred to Chapter VI, " Chemistry of Dairying," by Snyder. BUTTER 118. Composition. — Butter is made by the churning or agitation of cream and is composed mainly of milk fats and water, together with smaller amounts of ash, salt, casein, milk sugar, and lactic acid. Average butter has the following composition : Water . Ash and salt Casein and albumin Fat . . . Per Cent 10.5 2.5 I.O 86.0 When butter contains an abnormal amount of water, it is considered adulterated. According to act of Con- gress standard butter should not contain over i6 per cent of water nor less than 82.5 per cent of fat. 119. Digestibility of Butter. — Digestion experiments show that practically all of the fat, 98 per cent, is di- gestible and available for use by the body. Butter is valuable only for the production of heat and energy. Alone, it is incapable of sustaining life, because it con- tains no proteid material. It is usually one of the more expensive items of food, but it is generally considered quite necessary in a ration.^ It has been suggested 92 HUMAN FOODS AND THEIR NUTRITIVE VALUE that it takes an important part mechanically in the digestion of food. 120. Adulteration of Butter. — In addition to contain- ing an excess of water, butter is adulterated in other ways. Old, stale butter is occasionally melted, washed, salted, and reworked. This product is known as reno- vated butter, and has poor keeping qualities. Frequently preservatives are added to such butter to delay fermen- tation changes. Oleomargarine and butterine are made by mixing vegetable and animal fats.*" Highly colored stearin, cotton-seed oil, and lard are the usual materials from which oleomargarine is made. It has practically the same composition, digestibility, and food value as butter. When sold under its true name and not as butter, there is no objection, as it is a valuable food and supplies heat and energy at less cost than butter. The main objection to oleomargarine and butterine is that they are sold as butter. ''i The coloring of butter is not generally looked upon as adulteration, for butter naturally has a more or less yellow tinge. According to an act of Congress, butter colors of a non-injurious character are allowed to be used. CHEESE 121. General Composition. — Cheese is made by the addition of rennet to ripened milk, resulting in coagu- lation of the casein, which mechanically combines with MILK AND DAIRY PRODUCTS 93 the fat. It differs from butter in composition by con- taining, in addition to fat, casein and appreciable amounts of mineral matter. The composition varies with the character of the milk from which the cheese was made. Average milk produces cheese containing a larger amount of fat than proteids, while cheese from skimmed or partially skimmed milk is proportionally poorer in fat. Ordinarily there is about 35 per cent of water, 33 per cent of fat, and 27 per cent of casein, and albumin or milk proteids, the remainder being ash, salt, milk sugar, and lactic acid. Cheese is characterized by its large percentage of both fat and protein, and has high food value. It contains more fat and protein than any of the meats ; in fact, there are but few foods which have such liberal amounts of these nutrients as cheese. The odor and flavor of cheese are due to workings of bacteria which result in the production of aromatic com- pounds. The purity and condition of the milk, as well as the method of manufacture and the kind of ferment material used, determine largely the flavor and odor. Cheese is generally allowed to undergo a ripening or curing process before it is used as food. The changes resulting consist mainly in increased solubility of the proteids, with the formation of a small amount of amid and aromatic compounds."^ 122. Digestibility. — Cheese is popularly considered an indigestible food, but extended experiments show that it is quite completely digested, although in the case of 94 HUMAN FOODS AND THEIR NUTRITIVE VALUE some individuals not easily digested. In general, about 95 per cent of the fat and 92 per cent and more of the protein is digested, depending upon the general com- position of the cheese and the digestive capacity of the individual. As far as total digestibility is concerned, there appears to be but little difference between green and well-cured cheese. So far as ease of digestion is concerned, it is probable that some difference exists. There is also but little difference in digestibility result- ing from the way in which milk is made into cheese, the nutrients of Roquefort, Swiss, Camembert, and Cheddar being about equally digestible. ^^ The differences in odor and taste are due to variations in kind and amount of bacterial action. When combined with other foods, cheese may exercise a beneficial influence upon diges- tion in the same way as noted from the use of several foods in a ration. No material differences were ob- served in digestibility when cheese was used in small amounts, as for condimental purposes, or when used in large amounts to furnish nutrients. Artificial digestion experiments show that cheese is more readily acted upon by the pancreatic than by the gastric fluids, suggest- ing that cheese undergoes intestinal rather than gastric digestion. It is possible this is the reason that cheese is slow of digestion in the case of some individuals. 123. Use in the Dietary. — Cheese should be used in the dietary regularly and in reasonable amounts, rather than irregularly and then in large amounts. Cheese is MILK AND DAIRY PRODUCTS 95 not a luxury, but ordinarily it is one of the cheapest and most nutritious of human foods. A pound of cheese costing I s cents contains about a quarter of a pound of protein and a third of a pound of fat ; at the same price, beef yields only about half as much fat and less protein. Cheese at i8 cents per pound furnishes more available nutrients and energy than beef at 12 cents per pound. In the dietary of European armies, cheese to a great extent takes the place of beef. See Chapter XVI. 124. Cottage Cheese is made by coagulating milk and preparing the curd by mixing with it cream or melted butter and salt or sugar as desired. When milk can be procured at little cost, cottage cheese is one of the cheapest and most valuable foods.*^ 125. Different Kinds of Cheese. — By the use of dif- ferent kinds of ferments and variations in the process of manufacture different types or kinds of cheese are made, as Roquefort, Swiss, Edam, Stilton, Camembert, etc. In the manufacture of Roquefort cheese, which is made from goats' and ewes' milk, bread is added and the cheese is cured in caves, resulting in the formation of a green mold which penetrates the cheese mass, and produces characteristic odor and flavor. Stilton is an English soft, rich cheese of mild flavor, made from milk to which cream is usually added. It is allowed to un- dergo an extended process of ripening, often resulting in the formation of bluish green threads of fungus. Limburger owes its characteristic odor and flavor to the 96 HUMAN FOODS AND THEIR NUTRITIVE VALUE action of special ferment bodies which carry on the ripening process. Neufchatel is a soft cheese made from sweet milk to which the rennet is added at a high temperature. After pressing, it is kneaded and worked, and then put into packages and covered with tin foil. 126. Adulteration of Cheese. — The most common forms of adulteration are the manufacture of skim-milk cheese by the removal of the fat from the milk, and substitution of cheaper and foreign fats, making a prod- uct known as filled cheese. When not labeled whole milk cheese, or sold as such, there is no objection to skim-milk cheese. It has a high food value and is often a cheap source of protein. The manufacture of filled cheese is now regulated by the national government, and all such cheese must pay a special tax and be prop- erly labeled. As a result, the amount of filled cheese upon the market has very greatly decreased, and cheese is now less adulterated than in former years. The na- tional dairy law allows the use of coloring matter of a harmless nature in the manufacture of cheese. 127. Dairy Products in the Dietary. — The nutrients in milk are produced at less expense for grain and for- age than the nutrients in beef, hence from a pecuniary point of view, dairy products, as milk and cheese, have the advantage. In the case of butter, however, the cost usually exceeds that of meat. In older agricultural re- gions, where the cost of beef production reaches the MILK AND DAIRY PRODUCTS 97 maximum, dairying is generally resorted to, as it yields larger financial returns, and as a result more cheese and less beef are used in the dietary. As the cost of meats is enhanced, dairy products, as cheese, naturally take their place. CHAPTER VIII MEATS AND ANIMAL FOOD PRODUCTS 128. General Composition. — Animal tissue is composed of the same classes of compounds as plant tissue. In each, water makes up a large portion of the weight, and the dry matter is composed of nitrogenous and non- nitrogenous compounds, and ash or mineral matter. Plants and animals differ in composition not so much as to the kinds of compounds, although there are differences, but more in the percentage amounts of these compounds. In plants, with the exception of the legumes, the protein rarely exceeds 14 per cent, and in many vegetable foods, when prepared for the table, there is less than 2 per cent. In meats the protein ranges from 15 to 20 per cent. The non-nitrogenous compounds of plants are present mainly in the form of starch, sugar, and cellulose, while in animal bodies there are only traces of carbohy- drates, but large amounts of fat. Fat is the chief non- nitrogenous compound of meats ; it ranges between quite wide limits, depending upon kind, age, and general condition of the animal. Meats contain the same gen- eral classes of proteins as the vegetable foods ; in each the proteins are made up of albumins, glubulins, albu- MEATS AND ANIMAL FOOD PRODUCTS 99 minates, peptone-like bodies, and insoluble proteids. The larger portion of the protein of meats and cereals is in insoluble forms. The meat juices, which contain the soluble portion of the proteins, constitute less than 5 per cent of the nitrogenous compounds. Meats con- tain less amid substances than plants, in which the amids Fig. 26. — Meat and Extractive Substances. are produced from ammonium compounds and are sup- posed to be intermediate products in the formation of proteids, while in the animal body they are derived from the proteids supplied in the food and, it is generally be- lieved, cannot form proteids. Albuminoids make up the connective tissue, hair, and skin, and are more abun- dant in animal than in plant tissue. One of the chief albuminoids is gelatine. Both plant and animal foods 100 HUMAN FOODS AND THEIR NUTRITIVE VALUE undergo bacterial changes resulting in the production of alkaloidal bodies known as ptomaines, of which there are a large number. These are poisonous and are what cause putrid and stale meat to be unwholesome. The protein in meat differs little in general composition from that of vegetable origin ; differences in structure and cleavage products between the two are, however, notice- able. While meats from different kinds of animals have somewhat the same general composition, they differ in physical properties, and also in the nature of the various nutrients. For example, pork contains less protein than beef, but the protein of pork is materially different from that of beef, as a larger portion is in the form of soluble proteids, while in beef more is present in an insoluble form. Not only are differences in the percentage of individual proteins noticeable, but there are equally as great differences in the fats. As for example : some of the meats have a larger proportion of the fat as stearin than do others. Hence meats differ in texture and taste more than in nutritive value, due to the \'ariations in the percentage of the different proteins, fats, and extractive material, rather than to differences in the total amounts of these compounds. The taste and flavor of meat is to a large extent influenced by the amount of extractive material. While the nutrients of meats are divided into classes, as proteins and fats, there are a large number of sepa- rate compounds which make up each of the individual MEATS AND ANIMAL FOOD PRODUCTS lOI classes, and there are also small amounts of compounds which are not included in these groups. > 129. Beef. — About one half of the weight of beef is water; the lean meat contains a much larger amount J 0. s (^ , CO y -^••"i o^y% ■M-i ;v Fig. 27. — Standard Cuts of Beef. (From Office of Experiment Station Bulletin.) than the fat. As a rule, the parts of the animal that contain the most fat contain the least water. In some meats there is considerable refuse, 25 to 30 per cent. In average meat about 12 per cent of the butcher's weight is refuse and non-edible parts.** A pound of average butcher's meat is about one half water, and over I02 HUMAN FOODS AND THEIR NUTRITIVE VALUE ID per cent waste and refuse, which leaves less than 40 per cent fat and protein. Meat is generally con- sidered to have a high nutritive value, due to the com- paratively large amounts of fat and protein. Beef contains more protein than any vegetable food, except the legumes, and from i to 1.5 per cent mineral matter, exclusive of bone. Some of the mineral matter is chemi- cally united with the protein and other compounds. While figures are given for average composition of beef, it is to be noted that wide variations are frequently to be met with, some samples containing a much larger amount of waste and trimmings than others, and this influences the per cent of the nutritive substances. In making calculations of nutrients consumed, as in dietary studies, the figures for average composition of meat should be used only in cases where the samples do not contain an excess either of fat or trimmings.*" When very lean, there is often a large amount of refuse, and the meat contains less dry matter and is of poorer flavor than from animals in prime condition. In the case of very fat animals, a large amount of waste results, and the flavor is sometimes impaired. 130. Veal differs from beef in containing a smaller amount of dry matter, richer in protein, but poorer in fat. Animals differ in composition at different stages of growth in much the same way as plants. In the earlier stages protein predominates in the plant tissue, while later the carbohydrates are added in larger amounts, MEATS AND ANIMAL FOOD PRODUCTS 103 reducing the percentage content of protein. In animals the same is noticeable. Young animals are, pound for pound, richer in protein than old animals. While in the case of vegetables the increase in size, or rotundity, is due to starch and carbohydrates, in animals it is due to the addition of fat. But plants, like animals, observe the same general laws as to changes in composition at different stages of growth. Fig. 28. — Standard Cuts of Mutton. (From Office of Experiment Station Bulletin.) 131. Mutton. — There is about the same amount of refuse matter in mutton as in beef. In a side of mutton about 19 per cent are trimmings and waste, and in a side of beef 18.5 per cent. Mutton, as a rule, contains a little more fat and dry matter than beef, and some- what less protein. A side of beef, as purchased, con- 104 HUMAN FOODS AND THEIR NUTRITIVE VALUE tains about 50 per cent of water, 14.5 per cent protein, and 16.8 per cent of fat, while a side of mutton, as pur- chased, contains 42.9 per cent water, 12.5 per cent protein, and 24.7 per cent fat. A pound of beef yields a smaller number of calories by 25 per cent than a pound of mutton. At the same price per pound more nutrients can be purchased as mutton than as beef. The differences in composition between lamb and mutton are similar to those between veal and beef ; viz. a larger amount of water and protein and a smaller amount of fat in the same weight of the young animals. Differences in composition between the various cuts of lamb are noticeable. The leg contains the least fat and the most protein, while the chuck is richest in fat and poorest in protein. As in the case of beef, many of the cheaper cuts contain as much or more nutrients than the more expensive cuts. They are not, however, as palatable and differ as to toughness and other physi- cal characteristics. 132. Pork is characterized by a high per cent of fat and a comparatively low per cent of protein. It is gen- erally richest in fat of any of the meats. The per cent of water varies with the fatness of the animal ; in very fat animals there is a smaller amount, while lean ani- mals contain more. In lean salt pork there is about 20 per cent water, and in fat salt pork about 7 per cent. There is less refuse and waste in pork than in either beef or mutton. Ham contains from 14 to 15 per cent MEATS AND ANIMAL FOOD PRODUCTS 105 of refus'e, and bacon about 7 per cent. Bacon has nearly twice as much fat and a smaller amount of pro- tein than ham. A pound of bacon, as purchased, will yield nearly twice as much energy or fuel value as a pound of ham. Digestion experiments show that bacon is quite readily and completely digested and is often a ■M ^ { S'a.iJr _JP^^ (ji.rj\. £^ -y\'* R ^ ■Jffit d^\ -*(*: I te^ 1 Fig. 29. — Standard Cuts of Pork. (From Office of Experiment Station Bulletin.) cheaper source of fat and protein than other meats. There is about three times as much fat in bacon as in beef. When prepared for the table bacon contains from 40 to 50 per cent of fat. A pound of high grade, lean bacon furnishes from o.i to 0.3 of a pound of digest- ible protein and from 0.4 to 0.6 of a pound of digestible fat, which is about two thirds as much fat as is found in butter. Bacon contains nearly as much digestible Io6 HUMAN FOODS AND THEIR NUTRITIVE VALUE protein as other meats and from two to three times as much fat, making it, at the same price per pound, a cheaper food than other meats. In salt pork there is from 60 to 85 per cent of fat, and less protein than in bacon. The protein and fat of pork differ from those in beef not only in percentage amounts, but also in the nature of the individual proteins and fats. The com- position of pork varies with the nature of the food that is consumed by the animal. Experiments show that it is possible by judicious feeding in the early stages of growth to produce pork with the maximum of lean meat and the minimum of fat. After the animal has passed a certain period, it is not possible by feeding to materially influence the percentage of nutrients in the meat. The flavor, too, of pork, as of other meats, is dependent largely upon the nature of the food the animal consumes. When there is a scant amount of available protein in the ration, the meat is dry, nearly tasteless, and contains less of the soluble nitrogenous compounds which impart flavor and individuality. 133. Lard is prepared from the fat of swine, and is separated from associated tissue by the action of heat. A large amount of fat is found lining the back of the abdominal cavity, and this is known as leaf lard. Slight differences are noticeable in the composition and quality of lard made from different parts of the hog. Leaf lard is usually considered the best. Lard is com- posed of the three fats, olein, stearin, and palmatin, and MEATS AXD ANIMAL FOOD PRODUCTS I07 has a number of characteristic physical properties, as specific gravity, melting point, iodine absorption num- ber, as well as behavior with various reagents, and these enable the mixing of other fats with lard to be readily detected. Lard is used in the preparation of oleomargarine, and it is also combined with various vegetable oils, as cotton-seed oil, in the making of imita- tion or compound lards. *^ Lard substitutes differ little in general composition from pure lard, except in the structure of the crystals and the percentage of the vari- ous individual fats. 134. Texture and Toughness of Meats. — In discuss- ing the texture of meats. Professor Woods states : *^ "Whether meats are tough or tender depends upon two things: the character of the walls of the muscle tubes and the character of the connective tissues which bind the tubes and muscles together. In young and well-nourished aniinals the tube walls are thin and delicate, and the connective tissue is small in amount. As the ani- mals grow older or are made to work (and this is particularly true in the case of poorly nourished animals), the walls of the muscle tubes and the connective tissues become thick and hard. This is the reason why the flesh of young, well-fed animals is tender and easily masticated, while the flesh of old, hard-worked, or poorly fed animals is often so tough that prolonged boiling or roasting seems to have but little effect on it. " After slaughtering, meats undergo marked changes in texture. These changes can be grouped under three classes or stages. In the first stage, when the meat is just slaughtered, the flesh is soft, juicy, and quite tender. In the next stage the flesh stiffens and the meat becomes hard and tough. This condition is known as r/g-or mortis, and continues until the third stage, when the first changes of Io8 HUMAN FOODS AND THEIR NUTRITIVE VALUE decomposition set in. In hot climates the meat is commonly eaten in either the first or second stage. In cold climates it is seldom eaten before the second stage, and generally, in order to lessen the toughness, it is allowed to enter the third stage, when it becomes soft and tender, and acquires added flavor. The softening is due in part to the formation of lactic acid, which acts upon the connective tissue. The same effect may be produced, though more rapidly, by macerating the meat with weak vinegar. Meat is sometimes made tender by cutting the flesh into thin slices and pounding it across the cut ends until the fibers are broken." 135. Influence of Cooking upon the Composition of Meats. ""^ — It is believed by many that losses are pre- vented and the nutritive value conserved when, in the cooking of meat, it is placed directly into boiling water rather than into cold water and then brought to the boiling point and cooked. Extensive experiments have been made by Dr. Grindley in regard to this and other points connected with the cooking of meats, and in gen- eral it was found that the temperature of the water in w hich the meat w a s placed made l ittle difference in its nutritive value or the amount of mate rial extract ed. It was found that by both methods there was dissolved 2._'K per cent of the p r otein matte r, i per ^e nt of the nitrogenous extractives, 1.6 per cent of non-j Titrogenous material, and o^^j per cent of ash, of the raw meat, which was equivalent to about 13 per cent of the total proteid material and 81 per cent of the ash. The cold water extract contained bodies coagulated by heat. Cold water did not extract any of the fat, but during the pro- cess of cooking, appreciable amounts were lost mechani- MEATS AND ANIMAL FOOD PRODUCTS I09 cally. Cooked meats were found to be less soluble in cold water than raw meats. D uring- the process of boiling , meat shrinks in weight about 40 or 45 per cent , d epending mainly upon the size of the pieces and th e content of fa t. The loss in weight is practically a loss of water, and the loss of nutrients, all told, amounts to about 4 per cent, or more, depending upon the mechan- ical loss.''* But slight differences were found in the composition of the meats cooked three and five hour periods. ' " Careful study in this laboratory has shown that when meat is cooked in water at 80° to 85° C, placing meat in hot or cold water at the start has little effect on the amount of nutrients in the meat which passes into the broth. The meat was in the form of cubes, one to two inches, and in pieces weighing from one to two pounds. ■' It is commonly supposed that when meat is plunged into boiling water, the albumin coagulates and forms a crust, which prevents the escape of nutritive materials into the broth. It is also believed that if a rich broth is desired, to be used either as a soup or with the meat as a stew, it is more desirable to place the meat in cold water at the start. From the results of these experiments, however, it is evident( that, under these conditions, there can be little advantage in using) hot or cold water at the beginning. When meats were cooked by) I dry heat, as in roasting, a larger amount of nutrients was rendered soluble in water than during boiling. The losses of nutrients were much smaller when meats were cooked by dry heat than when cooked in water, being on the average, water 35 per cent, nitrogenous extrac- tives 9 per cent, non-nitrogenous extractives 17 per cent, fat 7 per cent, ash 12 per cent, and a small loss of protein." The nutrients in the broth of the meat started in hot water amounted to about i per cent of protein, no HUMAN FOODS AND THEIR NUTRITIVE VALUE I per cent of fat, and 0.5 per cent of ash, the amount of nutrients being directly proportional to the length of time and temperature of the cooking. In general, the larger the pieces, the smaller the losses. Beef that has been used in the preparation of beef tea loses its extrac- tive materials, which impart taste and flavor, but there is only a small loss of actual nutritive value. Clear meat broth contains little nutriment — less than unfiltered broth. Most of the nitrogenous material of the broth is in the form of creatin, sarkin, and xanthin, nitrogenous extractives or amid substances having a much lower food value than proteids. Experiments show that some of these extractives have physiological properties slightly stimulating in their action, and it is believed the stimulat- ing effect of a meat diet is in part due to these.*^ They are valuable principally for imparting taste and flavor, and cannot be regarded as nutrients. The variations in taste and flavor of meats from different sources are due largely to differences in extractive material. " In general, the various methods of cooking materially modify the appearance, texture, and flavor of meat, and hence its palatability, but have little effect on total nutritive value. Whether it be cooked in hot water, as in boiling or stewing, or by dry heat, as in roasting, broiling, or frying, meat of all kinds has a high food value, when judged by the kind and amount of nutrient ingredients which are present." "" Beef extrac ts of commerce contain about c,o per cent o f extracti ve matters, as amids, together with smaller amounts of soluble proteids ; ash, mainly added salt, is MEATS AND ANIMAL FOOD PRODUCTS III also present in liberal amounts (20 per cent). Beef extracts have condimental value imparting taste and flavor, which make them useful for soup stocks, but they furnish little in the way of nutritive substance. 136. Miscellaneous Meat Products. — By combining different parts of the same animal, or different meats, a large number of products known as sausage are made. These vary in composition with the ingredients used. In general, they are richer in fat than beef and contain about the same amount of protein. Potato flour and flovir from cereals are sometimes used in their prepara- tions, but the presence of any material amount, unless so stated on the package, is considered an adulter- ant. Pickled meats are prepared by the use of condiments, as salt, sugar, vinegar, and saltpeter. During the smok- ing and curing of meats, no appreciable losses of nutri- ents occur. ^^ The smoke acts as a preservative, and imparts condimental properties. Saltpeter (potassium nitrate) has been used from earliest times in the prepa- ration of meats ; it preserves color and delays fermenta- tion changes. When used in moderate amounts it cannot be regarded as a preservative or injurious to health. Excessive amounts, however, are objectionable. Smoked meats, prepared with or without saltpeter, give aprpreciable reactions for nitrites, compounds formed during combustion of the wood by which the meat was smoked. Many vegetables contain naturally much 112 HUMAN FOODS AND THEIR NUTRITIVE VALUE larger amounts of nitrates, taken from the soil as food, than meat that has been preserved with saltpeter.^^ 137. Poultry. — The refuse and waste from chickens, as purchased on the market, ranges from 15 to 30 per cent. The fat content is much lower than in turkeys or ducks, the largest amount being found in geese. The edible portion of all fowls is rich in protein, particularly the dark meat, and the food value is about equal to that of meat in general. When it is desired to secure a large amount of protein with but little fat, chicken supplies this, perhaps, better than any other animal food. A difference is observed in the composition of the meat of young and old fowls similar to that between beef and veal. The physical composition and, to a slight extent, the solubility of the proteids are altered by prolonged cold storage, the difference being noticeable mainly in the appearance of the connective tissue of the muscles. In discussing poultry as food, Langworthy states : ^^ "A good, fresh bird shows a well-rounded form, with neat, compact legs, and no sharp, bony angles on the breast, indicating a lack of tender white meat. The sl ^ .'H t^ a* H H H m Ch >£> -rt 00 IN H N W ^D ONmO n j \o iTi 1 O ■^ CJ N O 1 <^ 1 >-i [N 1 (N vJD tN30 ON )- o 1 ri.i>: 1 IT) in liTO ^ 1 in 1 10 TT 1 C^vO \D CO -t lONO OnnO "o j; M H M M )-( i-i M M IH H p ft u fc. rC (N H ^- -t rO fO 00 c> 00 IN -^ Tj- en -t ^ ^ ' " 1 M M m" M 6 1 H 1 d 1 M d d M d d d w M I D ^ i^ ^ K t^ rx H t^ en M M W 'O INOO 00 "^ m « W I CO d iH en ci 1 ^ rn 1 CO -1-00 tN w 00 Tt- d ci J u ' vOO ' MD Cv. o. c-^ c^ ' tN ' IN IN ' IN t^ IN t-^ « INOO (NIN PM O 1 1J^ IN « 1 in\D m ON CO ! ^ 1 °- M 1 tN U-)LOCO ro i-O On CO fc u 1 \dvd 1 H i-i M d M 1 M 1 Hi H 1 TJ-M d 4 d d d IN d ;^ c nj into o M up r^ M cr\ oc . ^ q 00 Tj- ON t-^ 00 HC H \0 ^ 1 ci «■ 1 00 od IN d>cd 1 "^ i ^ LO 1 NO MD MP C^ h" uS li-; ON H i:l. 1 ^^ c '5 cj 9 9^°9 oo 'O lOOO ON -^ ON Cn -1- -> ON Lo m en mm to -^00 m i_ en M M W M H H. M d W H ci M d H M H d M d d w H !^ ^ JD (J iJ^ Ov rn oo iNoo M rN. -^ r^ fv m Ti- M ^-1- xn 'iZ W M H « H d H ci d d « H d H CO M q tN ^ 6 \r, -t \n B fv. tN N C» CO IN z bn' *^ Onco i-i O vO CTi 10 00 lO ^ ^D 't Ci rn '^ w 5r1 M ro 4-0 IN \h N* d> IN r^ On -f d- in M u I^W >- lOO -o In IN t^ IN tN [N IN MD (N tN NO C-. tN Cn IN &. c -J U O N -t M t^OO -f- O -rt IN Tl- 00 M w tl- t-v O^ND ON mNO 00 q\ ^ lO t>. I>. N H H M W M M M H M M LO -rj- H 6 -IT) 6 d d 00 d H C^ a • « OO M M q\M « ^0 IN O yD Tj- 10 ■^ to r|- CJ NO c^ en ON « in Ti- L. M M d d oi M d d ci 00 vd 00 onoo d ci NO NO d en C^ 1 """ H « o m M 4J inw \£) M \q CT- vq M OvlO yD On NO LO On cni-i en n 00 en a ^ d ^°^ d d d od U-) d d •-: en d M ci d -t- -}- ci tNNO d t- W M H hH M -. M CN fii . S (U TH 'id 2 T3 X) ■-^ "ri^ ;^ ■ c ■ 1) ■ QJ P c o O rt OJ :^ -c T) O -S • o J8se ■5 ~ s * « . LI . Q^ O .CO . a , '0 P- 4[ \li\MTlill\h H H. UI.IK '■'■"■■'" '■■"- .',;;;,',":„ "irr:! "•'" «■■»"■ '"i-"- n.,„™k..„..pm 10 20 30 40 50 60 70 80 90 10 •■■"•■'"■ *'"■ 400 800 1200 1600 2000 2400 2800 3200.3600 401 Beet round Beet round' Beef! sirloin Beet sirloin' Beet rib Beet rib' Pork, spare rib Pork, salt mT^yna-afmsismBBBisBS/SKim Wheat bread Wheat Sour Com meal Oatmeal Beans, dried Rice Potatoes Fig. 56. — Composition of Foods. (From Office of Experiment Stations Bulletin.) COMPARATIVE COST AND VALUE OF FOODS 233 milk is 5 cents per quart, two quarts or approximately four pounds, can be procured for lO cents. If the milk contain fat, 4 per cent, protein, 3.3 per cent, carbo- hydrates, 5 per cent, and fuel value, 310 calories per pound, multiplying each of these by 4 gives the nutri- ents and fuel value in four pounds, or 10 cents worth of milk, as follows: Protein . Fat Carbohydrates Calories 0.13 lb. 0.16 lb. 0.2 lb. 1240 If it is desired to compare milk at 5 cents per quart with round steak at 15 cents per pound, 10 cents will procure 0.66, or two thirds of a pound of round steak containing on an average (edible portion) 19 per cent protein, 12.8 per cent fat, and yielding 890 calories per pound. If 10 per cent is refuse, there is edible about 0.6 of a pound. The amounts of nutrients in the 0.6 of a pound of steak, edible portion, or 0.66 lb. as pur- chased would be : Protein o.ii lb. Fat 0.08 lb. Calories .... . 534 It is to be observed that from the 10 cents' worth of milk a little more protein, 0.08 of a pound more fat, and nearly two and one half times as many calories can be secured as from the 10 cents' worth of meat. This is due to the carbohydrates and the larger amount of fat 234 HUMAN FOODS AND THEIR NUTRITIVE VALUE which the milk contains. At these prices, milk should be used liberally in the dietary, as it furnishes more of all the nutrients than does meat. It would not be ad- visable to exclude meat entirely from the ration, but milk at 5 cents per quart is cheaper food than meat at 15 cents per pound. In making comparisons, prefer- ence cannot always be given to one food because of its containing more of any particular nutrient, for often there are other factors that influence the value. 243. Comparing Foods as to Nutritive Value. — In general, preference should be given to foods which sup- ply the most protein, provided the differences between the carbohydrates and fats are not large. When the protein content of two foods is nearly the same, but the fats and carbohydrates differ materially, the preference may safely be given to the food which supplies the larger amount of total nutrients. A pound of protein in a ration is more valuable than a pound of either fat or carbohydrates, although it is not possible to establish an absolute scale as to the comparative value of these nutrients, because they serve different functional pur- poses in the body. It is sometimes necessary to use small amounts of foods rich in protein in order to se- cure a balanced ration ; excessive use of protein, how- ever, is not economical, as that which is not needed for functional purposes is converted into heat and energy which could be supplied as well by the carbohydrates, and they are less expensive nutrients. ^- FOOD AM) Dll^T. Charl ;5— I'WTMAliY W'ONOMV OF FOOD. AniiHiiits (if Xiiti-it^iits OliliiiiH<<) in DimiTiil l-'imtl .M,if,.|i,,ij, )nr 10 niit-^. I'niti-iii. FuK )'iiihiili\.lr.ili- Vii,.| v,||,„.. .Miii.-inl I ^^^^^m - -~ ^^^^^ miittci-^. IVin- r.-ii ■ i [HT «-.iit^(iin iViiiiiii»iiriiiitiii'iitMiii-- ILb. 2Lk 3Lk 4Lba 2000 CaJ. 4000 Cal. 6000 Cal 8000 Gal. Beet round 12 .83 SL BeeE sirloin 18 .55 ■■ Beef. lib 16 .63 ±i Mutton, leg 12 .83 ^ Pork, spare rib 12 83 JIL Pork, salt fat 14 ■" ^~ Ham. smoked 16 .63 SLt Codfish, fresh 8 1.25 . Codfish, salt 6 167 »' Oysters. 40 cts.qt 20 .50 \ Milk.6cts.qt 3 3.33 i±_ Buttor 24 .42 m^^ Cheese 16 .63 iS. Eggs, 25 cts. doz. 161 ,60 i Wheat bread 4 "" ""* Wheat fiour 21 '"^''"'' Com meal 2 5,00 ' Oatmeal 4 2.50 U^^...^.^ Beans, white, dried 4 250 '^^m^bhmi Rice 5 2.00 '" Potatoes,60ct&bush. 1 lOOO '.l^^m Sugar 5 200 ' -' w Fig. 57. — Pecuniary Economy of Food. (From Office of Experiment Stations BuUetin.) 235 236 HUMAN FOODS AND THEIR NUTRITIVE VALUE Ten Cents will Purchase : (From Farmer's Bulletin No 142, U. S. Dept. of Agr.) Total Price Weight Pro- Car- Kind of Food Material PER OF Food Fat bohy- Energy Pound Mate- rial tein drates Cents Pounds Pound Pound Pounds Calories Beef, sirloin . 25 0.40 0.06 0.06 410 Do . . . 20 0.50 0.08 0.08 — 515 Do . . . 15 0.67 O.IO O.II — 685 Beef, round 16 0.63 O.II 0.08 — 560 Do. 14 0.71 0.13 o.og — 630 Do 12 0.83 0.15 O.IO — 740 Beef, shoulder clod 12 83 013 0.08 — 59S Do . . . 9 I. II 0.18 O.IO 795 Beef, stew meat . . , 5 2.00 0,29 0.23 — 1530 Beef, dried, chipped , . . 25 0,40 O.IO 0.03 — 315 Mutton chops, loin . . 16 0.63 0.08 0.17 — 890 Mutton, leg . . . 20 0.50 0,07 0.07 — 445 Do 16 0.63 0.09 0.09 — 560 Roast pork, loin .... 12 0.83 O.II 0.19 — 1035 Pork, smoked ham 22 0.4S 0.06 0.14 735 Do 18 0.55 0.08 0.18 9'5 Pork, fat salt .... 12 0.83 02 0.68 2950 Codfish, dressed, fresh 10 1. 00 O.II 220 Halibut, fresh .... 18 0.56 0.08 0.02 265 Cod, salt 7 1-43 0.22 O.OI 465 Mackerel, salt, dressed 10 1. 00 0.13 0.20 ins Salmon, canned 12 0.83 0.18 O.IO 760 Oysters, solids, 50 cents per quart 25 0.40 0.02 — O.OI go Oysters, solids, 35 cents per quart IS 0.56 0.03 O.OI 02 125 Lobster, canned . . l8 0.56 O.IO 01 — ?25 Butter 20 0.50 O.OI 0.40 _ I7C5 Do . . ... 25 0.40 — 0.32 — 1365 Do 30 °-33 — 0.27 — II 25 Eggs, 36 cents per dozen 24 0.42 0.05 0.04 — 260 16 0.63 0.07 0.06 — 385 Eggs, J 2 cents per dozen . 8 r-2S 0.14 O.II — 770 Cheese 16 0.63 0.16 0.20 0.02 Iit5 Milk, 7 cents per quart . 34 2,85 0.09 O.II 0.T4 885 Milk, 6 cents per quart . . . 3 3-33 O.II 0,13 0.17 1030 Wheat flour 3 3-33 0.32 0.03 245 5440 Do 2.V 4.00 0-39 0.04 2.94 6:40 Corn meal, granular 2i 4.00 0.31 0.07 2.96 6540 Wheat breakfast food 7h 1-33 0.13 0.02 0.98 2235 Oat breakfast food . . . 7i 1-33 0.19 0.09 0.86 239s Oatmeal ... 4 2.50 0-34 0.16 1.66 4500 Rice 8 1-25 0.08 — 0.97 2025 Wheat bread .... 6 1.67 0.13 02 0.87 2000 Do . . S 2.00 0.16 0.02 1.04 2400 Do . . . 4 2 50 0.20 0,03 1.30 3000 Rye bread ... .. . ■ . 5 2.00 0.15 0..01. 1.04 2340 Beans, white, dried S 2.00 0.35 0.03 1,16 3040 COMPARATIVE COST AND VALUE OF FOODS 237 Total Price Weight Pro- Car- Kind of Food Material PER OF Food Fat bohy- Energy Pound Mate- rial drates Cabbage . . . 2i 4.00 0.05 O.OI 0.18 460 Celery .... 5 2.00 0.C2 — 0.05 130 Corn, canned 10 1. 00 6.67 0.02 O.IO O.OI O.OI 0.18 0.93 430 1970 Potatoes, 90 cents per bushel . Potatoes, 60 cents per bushel . I 10,00 0.15 O.OI 1.40 2950 Potatoes, 45 cents per bushel . J 13-33 0.20 O.OI 1.87 3935 Turnips . . I 10.00 0.08 O.OI 0-54 1200 Apples . . . li 6.67 0.02 0.02 0.65 1270 Bananas 7 1-43 O.OI O.OI 0.18 370 Oranges 6 1.67 COT — 0.13 250 Strawberries . 7 6 1.67 .01 O.OI 0.09 1.67 215 2920 Sugar It is to be noted in the table that, ordinarily, for the same amount of money the most nutrients can be ob- tained in the form of milk, cheese, sugar, and beans, corn meal, wheat flour, oatmeal, and cereals in bulk. While meats supply protein liberally, they fail to furnish car- bohydrates as the vegetables. As discussed in the chapter on Dietary Studies of Families, unnecessarily expensive foods are often used, resulting either in lack of nutrients or unbalanced rations. EXAMPLES 1. Compute the calories and the amounts of protein, fat, and car- bohydrates that can be procured for 25 cents in cheese selling for 18 cents per pound ; how do these compare with the nutrients in eggs at 20 cents per dozen ? 2. Which food furnishes the larger amount of nutrients, potatoes at 50 cents per bushel or flour at $6 per barrel ? 3. How do beans at 10 cents per quart compare in nutritive value with beef at 1 5 cents per pound ? 4. How does salt codfish at lo cents per pound compare in nu- tritive value with lamb chops at 15 cents per jjound ? 5. Compare in nutritive value cream at 25 cents per quart with butter at 30 cents per pound. 6. Calculate the composition and nutritive value of a cake made of sugar, 8 oz. ; butter, 4 oz. ; eggs, 8 oz. ; flour, 8 oz. ; and milk, 4 oz. ; the baked cake weighs one and three fourths pounds. 238 HUMAN FOODS AND THEIR NUTRITIVE VALUE Average Composition of Common American Food Products (From Farmer's Bulletin, No. 142, U. S. Dept. of Agr.) Food Materials (as purchased) ANIMAL FOOD Beef, fresh : Chuck ribs Flank Loin Porterhouse steak Sirloin steak Neck Ribs Rib rolls Round Rump Shank, fore Shoulder and clod Fore quarter Hind quarter Beef, corned, canned, pickled, dried Corned beef Tongue, pickled Dried, salted, and smoked Canned boiled beef Canned corned beef Veal: Breast Leg Leg cutlets Fore quarter Hind quarter Mutton : Flank Leg, hind Loin chops Fore quarter Hind quarter, without tallow . . . . Lamb : Breast Leg, hind % 16.3 10.2 13-3 12.7 12.8 27.6 20,8 7.2 20.7 36-9 16.4 18.7 iS-7 8.4 6.0 4-7 21.3 14.2 34 24-5 20.7 9-9 18.4 16.0 21.2 17.2 19.1 174 % 52.6 54 -o 52-S 52.4 54-0 45-9 43.8 63-9 60.7 45-0 42.9 56.8 49.1 5°4 49,2 589 53-7 51-8 51-8 52.0 60.1 68.3 54-2 56.2 39-0 Si-2 42,0 41.6 454 45-5 529 % 15-5 17.0 16. 1 19.1 16.5 14-5 13-9 19-3 19.0 13-8 12.8 16.4 14-5 154 14-3 11.9 26.4 25-5 26.3 154 15-5 20.1 I5-I 16.2 13.8 iS-i 13-5 12.3 13-8 154 15 .9 % 15-° 19.0 17-5 17.9 16. 1 11.9 21.2 16.7 7-3 9.8 17-5 18.3 23.8 19.2 6.9 22.5 18.7 11. 7-9 7-5 6.0 6.6 36-9 147 28.3 245 23.2 19. 1 13,6 % 0.8 0.7 0.9 0.8 0.9 0.7 0.7 0.9 i.o 0.7 0.6 0.9 0.7 0.7 4.6 4-3 8.9 1-3 4.0 0.8 0,9 1.0 0.7 0.6 0.8 0.7 0.7 0.7 0.8 0.9 COMPARATIVE COST AND VALUE OF FOODS 239 Average Composition of Common American Food Products — Continued Food Materials (as purchased) ANl^■AT. FOOD — continued Pork, fresh : Ham , Loin chops , Shoulder Tenderloin , Pork, salted, cured, pickled : Ham, smoked , Shoulder, smoked , Salt pork , Bacon, smoked Sausage : Bologna , Pork Frankfort , Soups : Celery, cream of Beef Meat stew Tomato Poultry : Chicken, broilers , Fowls , Goose , Turkey Fish : Cod, dressed , Halibut, steaks or sections . . Mackerel, whole , Perch, yellow dressed , Shad, whole Shad, roe Fish, preserved : Cod, salt Herring, smoked Fish, canned Salmon Sardines td Z > Id ^-^ Id U h H >; a < s fc < (2i ■^ ^ > X % % % % % % 10.7 48.0 13-5 25-9 — o.S 19.7 41.8 13-4 24.2 — 0.8 12.4 44-9 12.0 29-8 — 0.7 6b.5 18.9 13-0 I.O 13.6 34.8 14.2 33.4 — 4.2 3S.2 3b.B 13.0 26.6 5-5 7-9 1-9 86.2 — 3-9 7-7 17.4 9-1 62.2 — 4-1 33 5';-2 18.2 19.7 — 3-8 — 39-8 13.0 44.2 I.I 2.2 — 57-2 19.6 18.6 l.I 3-4 88.6 2.1 2.8 S.o !■■; — 92.9 4-4 0.4 I.I 1.2 — 84-S 4.b 4-3 .s-.s I.I — 90.0 1.8 I.I 5-6 i-S 41.6 43-7 12.8 1-4 — 0.7 2^.q 47-1 13-7 12.3 — 0.7 I7.b 38.^; 134 29.8 — 0.7 22.7 42.4 ib.i 18.4 — 0.8 29.9 58.S II. I 0.2 — 0.8 17.7 61.9 IS -3 4-4 — 0.9 44-7 40.4 10.2 4.2 ■ — 0.7 35-1 S0.7 12.8 C.7 — 0.9 50.1 3S-2 9.4 4.8 — 0.7 — 71.2 20.9 3« 2.0 I-S 24.9 40.2 16.0 0.4 — I8.S 444 19.2 20.5 8.8 — 7-4 — 63.5 21.8 12. 1 — 2.6 *5.o 53-0 237 12. 1 ~ 5-3 * Refuse, oil. 240 HUMAN FOODS AND THEIR NUTRITIVE VALUE Average Composition of Common American Food Products — Continued Food Materials (as purchased) ANIMAL FOOD — continued Shellfish : ' Oysters, solids Clams Crabs Lobsters Eggs; Hen's eggs Dairy products, etc. : Butter Whole milk Skim milk Buttermilk Condensed milk Cream Cheese, Cheddar Cheese, full cream VEGETABLE FOOD Flour, meal, etc. : Entire wheat flour Graham flour Wheat flour, patent roller process High-grade and medium Low grade Macaroni, vermicelli, etc , Wheat breakfast food Buckwheat flour Rye flour Corn meal , Oat breakfast food Rice , Tapioca , Starch , Bread, pastry, etc. : White bread , Brown bread , % 52-4 61.7 '11.2 % 88.3 80.8 30-7 65-5 II. o 87.0 90s 91.0 26.9 74.0 27.4 34-a 11.4 "3 12 o 12.0 10.3 9.6 13.6 12.9 12.5 7-7 12.3 II. 4 35-3 43-6 6.0 10.6 7-9 5-9 131 I o 3-3 3-4 3° 8.8 2-5 27.7 25-9 13.8 13-3 11,4 14.0 13-4 12. 1 6.4 6.8 9.2 16 7 8.0 0.4 9.2 5-4 % 1-3 I.I 0.9 0.7 9-3 85.0 4.0 0-3 o-S 8-3 18.S 36.8 33'7 1-9 i.o 1-9 0.9 1.8 1.2 0.9 1-9 7-3 0-3 0.1 1-3 1.8 % 3-3 S-2 0.6 0.2 5° 51 4.8 54 I 45 4-1 2.4 71.9 71-4 75-1 71.2 74-1 75-2 77-9 78.7 7.'^ -4 66.2 79.0 88.0 90,0 53-1 ' 47-1 % i.i 23 i-S 0.8 09 30 0.7 0.7 0.7 1-9 o-S 4.0 3-8 I o 18 OS 0.9 1-3 1-3 0.9 0.7 1.0 2.1 0.4 0.1 I.I 2.1 Refuse, shell. COMPARATIVE COST AND VALUE OF FOODS 24I Average Composition of Common American Food Products — Continued Food Materials (as purchased) VEGETABLE FOOD — Continued Bread, pastry, etc. . Graham bread Whole wheat bread Rye bread Cake Cream crackers Oyster crackers Soda crackers Sugars, etc. : Molasses Candy* Honey Sugar, granulated Mapie sirup Vegetables : f Beans, dried Beans, Lima, shelled Beans, string Beets Cabbage Celery Corn, green (sweet) , edible portion Cucumbers Lettuce Mushrooms Onions Parsnips Peas (Pisum sativum), dried Peas \Pisu7n sativum) ^ shelled. . . . Cowpeas, dried Potatoes 7.0 20.0 150 20.0 15.0 15.0 10. o 20 o % 35-7 38-4 35-7 19.9 6.8 4.8 5-9 12.6 68.5 83.0 70.0 77-7 75-6 75-4 81. 1 80.5 88.1 78.9 66.4 9-5 74.6 13.0 62.6 % 8.9 9-7 9.0 6.3 9-7 "•3 9.8 22.S 7-1 2.1 1-3 1-4 0.9 3-1 0.7 i.o 35 1.4 1-3 24.6 7.0 21.4 % 1.8 0.9 0.6 9.0 12.1 10.5 9-1 0.7 0-3 0.1 0.2 0.1 I.I 0,2 0.2 0.4 0-3 0.4 1.0 0-5 1.4 0.1 S2-I 49-7 53-2 633 69.7 70s 73-1 70.0 96.0 81.0 lOO.O 71-4 59-6 22.0 6.9 7-7 4.8 2.6 19.7 2.6 2.q 6.8 8.9 10.8 62.0 16.9 60.8 14-7 % 1-5 1-3 1-5 i-S 1-7 2.9 2.1 3-5 1-7 0.7 0.9 0.9 0.8 0.7 0.4 0.8 1.2 0.5 I.I 2.9 1.0 3-4 >& Calo- ries "95 1 130 1 170 1630 1925 19 10 1875 1225 1680 1420 1750 1250 1520 540 170 160 "5 65 440 ^$ 65 185 190 230 1565 440 I5°S 29s * Plain confectionery not containing nuts, fruit, or chocolate. t Such vegetables as potatoes, squash, beets, etc., have a certain amount of inedible material, skin, seeds, etc. The amount varies with the method of preparing the vege- tables, and cannot be accurately estimated. The figures given for refuse of vegetables, fruits, etc., are assumed to represent approximately the amount of refuse in these foods as ordinarily prepared. 242 HUMAN FOODS AND THEIR NUTRITIVE VALUE Average Composition of Common American Food Products — Continued Food Materials (as purchased) VEGETABLE FOOD - - conii tilted Vegetables : Rhubarb Sweet potatoes Spinach Squash Tomatoes Turnips Vegetables, canned: Baked beans Peas {Fisu?n sativum), gieen Corn, green Succotash Tomatoes Fruits, berries, etc., fresh : * Apples Bananas Grapes Lemons .^ ; 30.0 Muskmelons .' 50.0 Oranges 27.0 Pears 10. o Persimmons, edible portion — Raspberries — Strawberries 5.0 % 40.0 20 o So.o 30.0 25.0 35-0 2S.O Watermelons Fruits, dried : Apples Apricots Dates 59-4 % 56.6 92 44 94 62, % 0.4 1.4 2.1 0.7 0.9 0.9 6.9 3-6 2,8 3-6 1.2 0-3 0.8 i.o 07 0-3 0.6 °-5 0.8 1.0 0.9 0.2 1.6 4-7 1-9 % 0.4 0.6 0-3 0.2 04 0.1 2.5 0.2 1.2 1.0 0.2 0-3 0.4 1.2 0-5 0.1 0.4 0.7 2.2 21.9 3.2 4-5 3-9 S-7 19.6 9.8 19,0 18.6 4.0 10.8 143 14.4 5-9 4.6 , 8-5 i 127 31 5 i 12.6 0.6 7.0 o. I i 2.7 2,2 I 66.1 1.0 62.5 2.5 70.6 % 0.4 0.9 2.1 0.4 o-S 0.6 2.1 I.I 0.9 0.9 0.6 03 0.6 0.4 0.4 0-3 0.4 0.4 0.9 0.6 0.6 0.1 2.0 2-4 1.2 Calo- ries 60 440 95 ICO 100 120 555 235 430 425 95 190 260 295 125 80 150 230 550 220 150 50 1185 1 125 1275 * Fruits contain a certain proportion of inedible materials, as skin, seeds, etc., which are properly classed as refuse. In some fruits, as oranges and prunes, the amount rejected in eating is practically the same as refuse. In others, as apples and pears, more or less of the edible material is ordinarily rejected with the skin and seeds and other inedible portions. The edible material which is thus thrown away, and should properly be classed with the waste, is here classed with the refuse. The figures for refuse here given represent, as nearly as can be ascertained, the quantities ordinarily rejected. comparative cost and value of foods 243 Average Composition of Common American Food Products — Continued Food Materials (as purchased) 3g VEGETABLE FOOU — C07ltfntted Fruits, dried : figs Raisins Nuts: Almonds Brazil nuts Butternuts Chestnuts, fresh Chestnuts, dried Cocoanuts Cocoanut, prepared Filberts Hickory nuts , Pecans, polished Peanuts Pinon {Pinus edulis) Walnuts, black Walnuts, English Miscellaneous : Chocolate Cocoa, powdered Cereal coffee, infusion fi part boiled in 20 parts water)f % lo.o 450 49.6 86.4 16 o 24.0 *48.8 S2-1 62.2 53-2 24-S 40.6 74-1 58.1 18.8 I3-I 2.7 2.6 0.6 37.8 4-5 7.2 3-5 1.8 1.4 1-4 6.9 2.0 0.6 i.o 5-9 4.6 98.2 4-3 2-3 ii-S 8.6 3-8 S-2 8.1 2.9 6.3 7-S 5-8 5-2 19-5 8.7 7.2 6.9 12.9 21.6 % 0-3 3-0 30.2 33-7 8.3 4-5 5-3 259 57-4 3'-3 25-5 33-3 29.1 36.8 14.6 26.6 48.7 28.9 74.2 68.5 9-S 3-5 °-S 35-4 564 14-3 31-5 6.2 43 6.2 18.S 10.2 30 6.8 30-3 37-7 1-4 % 2.4 3-1 I.I 2.0 0.4 I.I 17 0.9 1-3 I.I 0.8 0.7 1-5 1-7 0-5 0.6 7.2 Calo- ries 1280 1265 1515 1485 385 915 1385 1295 2865 1430 1 145 1465 177s 1730 730 1250 5625 2160 30 * Milk and shell. t The average of five analyses of cereal coffee grain is : Water 6.2, protein 13.3, fat 3.4, carbohydrates 72.6, and ash 4.5 per cent. Only a portion of the nutrients, however, enter into the infusion. The average in the table represents the available nutrients in the beverage. Infusions of genuine coffee and of tea like the above contain practically no nutrients. CHAPTER XVII DIETARY STUDIES 244. Object of Dietary Studies. — The quantity of food which different families purchase varies between wide limits ; a portion being lost mechanically in preparation and a still larger and more variable amount in the ref- use and non-edible parts. If a record is made of all foods purchased and the waste and non-edible portions are deducted, the nutrients consumed by a family may be calculated by multiplying the weight of each food- by the average composition. If such calculations be made, it will be found that in some families nearly a half pound per day of both protein and fat is consumed by adults, while in other families less than half of this amount is used. The object of dietary studies is to de- termine the source, cost, composition, and nutritive value of the foods consumed by different families; they also enable comparisons to be made of the amounts of nu- trients purchased. Extensive dietary studies have been made by the United States Department of Agriculture, and the results have been published in various bulletins.'^ 245. Wide and Narrow Rations. — When the amount of carbohydrates in a ration is small in comparison with the protein, it is called a narrow ration, while a wide ration is one in which the carbohydrates are much in ex- 244 DIETARY STUDIES 245 cess of the protein. When a ration contains 0.40 of a pound of protein, 0.40 of a pound of fat, and i pound of carbohydrates, it has a nutritive ratio of i to 4.8 and is a narrow ration. To calculate the nutritive ratio, the fat is multiplied by 2|, the product added to the carbohydrates, and this sum divided by the protein. It is not possible to designate accurately the amount of protein and other nutrients that should be in the daily ration of all persons, because the needs of the body vary so with different individuals. Hard and fast rules governing the amounts of nutrients to be consumed cannot as yet be formulated, as our knowledge of the subject is too limited. It is known that both excessive and scant amounts are alike injurious. While the appe- tite may indicate either hunger or satiety, it alone can- not always be relied upon as a safe guide for determining the amount and kind of food to consume, although the demands of appetite should not be disregarded until it has been demonstrated beyond a doubt that it is not voicing the needs of nature. There has been a tendency which perhaps was a survival of the Puritanical ideas of the early days to stamp as hurtful whatever seemed desirable and pleasant ; as examples might be cited the craving for water by fever patients, and for sugar by growing children, which have now been proven to be normal demands of nature. 246. Dietary Standards. — As a result of a large num- ber of dietary studies and digestion experiments, dietary 246 HUMAN FOODS AND THEIR NUTRITIVE VALUE standards have been prepared. Atwater in this coun- try and Voit in Germany have proposed such standards for men employed at different kinds of labor, as follows : z £ Carbohy- drates S 3 [I] > lb lb. lb. Calories Ratio Man with little ph3'sical exercise . 0.20 0.20 0.66 2450 5-5 Man with light muscular work . 0.22 0.22 0.77 2800 5-7 Man with moderate muscular woi'k 0.28 0.28 099 3520 q.S Man with active muscular work . o.si o■^^ 1. 10 4060 ,.6 Man with hard muscular work . 0-39 0.55 1-43 5700 6.9 In the table it will be seen that the quantity of nu- trients increases with the labor to be performed. In order to secure the necessary heat and energy, rations for rtien at heavy labor contain proportionally more fat and carbohydrates than are required for light work. All dietary standards, however, should be regarded as tentative only. Opinions differ greatly on different points ; for example, as to the amount of protein a ration should contain. This is a matter that can be deter- mined only from extended investigations under a variety of conditions, and as yet results are too meager to for- mulate other than tentative standards. Chittenden has found that the body can be sustained on very much less protein than is called for in the standard ration.'^ The amount of protein in the ration should be ample to sustain the body weight and maintain a nitrogen ~^- FOOD AXl) DIET. Cha.-l 4— DIKTAI.'IHS AM) I)1KTA1I\ STA.NDAKDS. 1)1 ivnTii> iir \i mtwh .wn k\kiii;v i\ pjiiii i'kii mw mi mv. Niiliiln.- iii-nMiiciil, (,i<1iiiil ii.nii.-iitN), Kii.'l mill,.. Underfed laborers, Italy ■ Students, Japan Lawyer. Germany Physiciaa Germany Physician. Denmark WeO-fed tailor. England Laborers at active work. England Well-paid mechanics, Germany Miners at severe work Prussia Mechanics at moderate work. Sweden Mechanics at severe work. Sweden Jlhemist Connecticut College professor, Connecticut _ College students Northern State s Ma^on, Connecticut " Glasblower. Mmchusetts^ Blacksmith. Comiecticut Factory operatives, Massachusetts Brickmaker at hai'd^work Massachusetts" Machinist at hard work, faachusetts Uirtsiry sliiiiiliiDls. Man with Me muscular work _Man at moderate work Man at severe work 1 Lh 2 Lbs 3 Lbs. ^ 2000 Cal 4000 CaJ. 6000 Cal -4 Fig. s8. — Dietaries and Dietary Standards. (Trom Office of Experiment Stations Bulletin.) 247 248 HUMAN FOODS AND THEIR NUTRITIVE VALUE equilibrium ; that is, the income and outgo of nitrogen from the body should be practically equal. "While one freely admits that health and a large measure of muscular strength may be maintained upon a minimum supply of protein, yet I think that a dispassionate survey of mankind will show that races which adopt such a diet are lacking in what, for want of a better word, one can only describe as energy." ^' On the other hand, excessive and unnecessarily large amounts of protein are sometimes consumed, adding greatly to the cost of the ration and necessitating ad- ditional labor on the part of the body for its elimination. 247. Number of Meals per Day. — Some persons ad- vocate two meals per day rather than three, but dietary studies show that the best results are secured when the food is divided among three rather than two meals, and with a two-meal system the tendency is to con- sume a larger total amount of food than when three meals are eaten. It is not essential that the food be equally divided among the three meals. Any one of them may be lighter or more substantial as the habits and inclinations of the individual dictate. If it is found necessary to reduce the total quantity of food consumed, this may be done by a proportional reduction of each of the meals, or of any one of them instead of de- creasing the number of meals per day. The occasional missing of a meal is sometimes beneficial, in cases of digestion disorders, but the ordinary requirements of persons in normal health who have either mental or DIETARY STUDIES 249 physical labor to perform are best met when three meals per day are consumed, as this insures an even supply of nutrients. For persons of sedentary habits, the kind and quantity of food at each meal must be regulated largely by the individual from knowledge based on personal experience. " In the matter of diet every man must, in the last resort, be a law unto himself; but he should draw up his dietetic code intelligently and apply it honestly, giving due heed to the warnings which nature is sure to address to him should he at any time transgress." ^ If there is trouble in digesting the food, it is well to study the other habits of life along with the food question, for it may be the difficulty arises from some other cause, and would be remedied by more exercise and fresh air, avoiding rush immediately after meals, more thorough mastication, or less worry. It is a serious matter to shut off the supply of food from a person not suffering from some disease and who is working ; as well cut off the supply of fuel from a furnace and then expect a full amount of energy and heat. But unlike the furnace, when the human body is deprived of needed nutrients it preys upon itself and uses up its reserve that should be drawn upon only in cases of illness or extreme nervous strain. Some persons live in such a way as to never have any reserve of strength and energy to call upon but use up each day all the body can pro- duce and so become physical bankrupts when they should be in their prime. Food is required for the 250 HUMAN FOODS AND THEIR NUTRITIVE VALUE production of nerve energy as well as physical en- ergy .78 248. Mixed Dietary Desirable. — Experiments in the feeding of farm animals show that the best results come from the combination of a number of foods to form a mixed ration, rather than from the use of one food alone/^ for in this way the work of digestion is more evenly distributed, and a higher degree of efficiency is secured from the foods consumed. The same is true in human feeding ; the best results are secured from a mixed diet. Ordinarily, about two fifths of the nutrients of a ration are derived from animal and three fifths from vegetable sources. 249. Animal and Vegetable Foods ; Economy of Pro- duction. — Animal foods can never compete in cheapness of the nutrients with cereals and vegetables, as it takes six to eight pounds or more of a cereal, together with forage crops, to make a pound of meat. Hence the re- turns in food value are very much larger from the direct use of the cereals as human food, than from the feeding of cereals to cattle and the use of the meat. As the population of a country increases, and foods necessarily become more expensive, cereals are destined to replace animal foods to a great extent, solely as a matter of economy. 250. Food Habits. — Long-established dietary habits and customs are not easily changed, and when the body becomes accustomed to certain foods, substitution DIETARY STUDIES 251 of Others, although equally valuable, may fail to give satisfactory results. For example, immigrants from southern Europe demand foods with which they are familiar, as macaroni, olive oil, and certain kinds of cheese, foods which are generally imported and more expensive than the staples produced in this country,^" and when they are compelled to live on other foods, even though they have as many nutrients, they complain of being underfed. Previously acquired food habits appear to affect materially the process of digestion and assimilation. Sudden and pronounced change in the feeding of farm animals is attended with unsatisfactory results, and whenever changes are made in the food of either humans or animals they should be gradual rather than radical. 251. Underfed Families. —As the purchasing of food is often done by inexperienced persons, palatability rather than nutritive value is made the basis of choice. Dietary studies show that because of lack of knowl- edge of the nutritive value of foods, whole families are often underfed. Particularly is this true where the means for purchasing foods are limited. In dietary studies among poor families in New York City,^^ the United States Department of Agriculture notes: "It is quite evident that what is needed among these families more than anything else is instruction in the way to make the little they have go the farthest." Some classes of the rich too are equally liable to be 252 HUMAN FOODS AND THEIR NUTRITIVE VALUE underfed, as they are more prone to food notions and are able to indulge them. Among the children of the rich are found some as poorly nourished as among the poor. 252. Cheap and Expensive Foods. — Among the more expensive items of a ration are meats, butter, and canned fruits. The difference in composition and nutritive value between various cuts of meat is small, being largely physical, and affecting taste and flavor rather than nutritive value. Expensive cuts of meat, high- priced breakfast cereals, tropical fruits and foods which impart special flavors, add little in the way of nutritive value to the ration, but greatly enhance the cost of liv- ing. Ordinarily the cheapest foods are corn meal, wheat flour and bread, milk, beans, cheese, sugar, and pota- toes." The amount of animal and vegetable foods to combine with these to form a balanced ration may be governed largely by personal preference or cost, as there is little difference in nutritive value. The selec- tion of foods on the basis of cost and nutritive value is discussed in Chapter XVI. 253. Food Notions. — Many erroneous ideas exist as to the nutritive value of foods, and often wholesome and valuable foods are discriminated against because of prejudice. Skim milk is usually regarded as containing little if any nourishing material, when in reahty it has a high protein content, and can be added to other foods to increase their nutritive value. The less expensive cuts DIETARY STUDIES 253 of meat contain more total nutrients than many of the more expensive ones. Beef extracts have been errone- ously said to contain more nutrients than beef,^' and mushrooms to be equal in value of beefsteak ; chemical analyses fail to confirm either statement. The banana also has been overestimated as to food value, and while it contains more nutrients than many fruits, it is not the equal of cereals, as has been claimed. ^^ Cocoa, although a valuable beverage, adds but Httle in the way of nu- trients to a ration unless it is made with milk. The value of a food should be based upon its composition as determined by chemical analysis, its digestibility as founded upon digestion experiments, and its palatabiUty and mechanical structure. Food notions have, in many instances, been the cause of banishing from the dietary wholesome and nutritious foods, of greatly increasing the cost of living, as well as of promulgating incorrect ideas in regard to foods, so that individuals and in some cases entire families have suffered from improper or in- sufficient food. 254. Dietary of Two Families Compared. — A dietary study often reveals ways in which it is possible to im- prove the ration in kinds and amounts of food, and sometimes at less expense. The following dietaries of two families for the same period show that one family expends over twice as much in the purchase of foods as the other family, and yet the one whose food costs the less actually secures the larger amount of nutritive 2 54 HUMAN FOODS AND THEIR NUTRITIVE VALUE material and is better fed than the family where more money is expended for food.^^ Food Consumed, One Week 20 loaves of bread . f I 00 10 to 12 lb. loin steak, or meat of similar cost 2.00 20 to 25 lb. rib roast, or similar meat . 440 4 lb. high-priced cei eal breakfast food, 20 ct. 0.80 Cake and pastry purchased 3.00 8 lb. butter, 30 ct. . 2.40 Tea, coffee, spices, etc. 0.75 Mushrooms . 0-75 Celery . . 1. 00 Oranges . 2.00 Potatoes . 0.2S Miscellaneous canned goods ... 2.00 Milk . . 0.50 Miscellaneous foods . 2.00 3 doz. eggs . . 0.60 Family No. 2 52345 15 lb. flour, bread home- made (skim milk used) 10-45 Yeast, shortening and skim milk O.IO 10 lb. steak (round. Ham- burger, and some loin) 1.50 10 lb. other meats, boil- ing pieces, rump roast. etc 1. 00 5 lb. cheese, i6 cents . . 0.80 S lb. oatmeal (bulk) O.I? 5 lb. beans . . . . 0.25 Home-made cake and pastry . . . 1. 00 6 lb. butter, 30 ct. . . 1.80 3 lb. home-made shorten- ing 0.25 Tea, coffee, and spices 0.40 Apples . . . 0.50 Prunes 0.25 Potatoes . ... 0.25 Milk 1. 00 .Miscellaneous foods . . 1. 00 3 doz. eggs 0.60 $'l .30 DIETARY STUDIES 25s FAMILY No. 20 lb. bread 10 lb. loin steak 20 lb. rib roast 4 lb. cereals 8 lb. butter 25 lb. potatoes 20 lb. milk T^.'/-r7J777r/r7/r77/A Protein .... Fat Carbohydrates FAMILY No. ^ 15 lb. flour i„>>,jj„ff,fjxm 5 lb. skinfi milk ^ 10 lb. round steak \ ^//»/////// 77i— 10 lb. beef r//////////^ 5 lb. cheese Yi/////i///A rz: 5 lb. oatmeal 6 lb. butter 3 lb. shortening 3 lb. prunes 25 lb. apples 25 lb. potatoes 40 lb. milk 5 lb. beans Fig. 59. — Cost and Nutritive Value of Rations. In comparing the foods used by the two families, it will be observed that family No. i purchased their bread at the bakery at a cost of ;^ i.oo, while the bread of family No. 2 was home-made, skim milk being used in 2S6 HUMAN FOODS AND THEIR NUTRITIVE VALUE its preparation, the flour, milk, yeast, and shortening cost- ing about 55 cents. Family No. i consumed lo pounds of expensive steaks, family No. 2 consumed the same number of pounds, a portion being cheaper cuts. In- stead of the 20 pounds of roast or similar beef used by family No. i, only one half as much and cheaper cuts as boiling pieces, stew, rump roast, etc., were used by family No. 2 ; 5 pounds of beans and 5 pounds of cheese taking the place of some of the meat. Family No. i consumed 4 pounds of high-priced cereal breakfast foods, supposing they contained a larger amount of nutrients than were actually present. In place of the 4 pounds of high-priced cereal breakfast foods of family No. i, family No. 2 used 5 pounds of oatmeal purchased in bulk. Family No. i bought their cake and pastry for ;?3.oo, while those of family No. 2 were home made and cost $1.00. Family No. 2 used 2 pounds less butter per week because of the preparation and use of home-made shortening from beef suet and milk. They also pur- chased a smaller amount of tea, coffee, and spices than family No. i. Family No. 2 consumed a larger quantity of less expensive fruits and vegetables than family No. i, who ate 75 cents' worth of mushrooms with the idea that they contained as much protein as meat, but analyses show that mushrooms contain no more nutrients than potatoes and similar vegetables. In place of the celery and oranges, apples and prunes were used by family No. 2. The same amount of potatoes was used by each. Fifty cents was spent for milk by family No. i and DIETARY STUDIES 257 $i.oo by family, No. 2. The total amount expended for food by family No. i was ^23.45, while family No. 2 purchased a greater variety of foods for ^11.30, as well as foods containing more nutrients. The approximate amounts of nutrients in the foods purchased by the two families are given in the following table, from which it will be observed that family No. 2 obtained a much larger amount of total nutrients and was better fed at considerably less expense than family No. i. Nutrients in Foods Consumed. — Family No. i Protein Lb. F.T Lb. Carbohydrates Lb. 20 lb. bread . . 10 lb. loin steak . . . . _. 20 lb. rib roast 4 lb. cereals .... 8 lb. butter 25 lb. potatoes . 20 lb. milk . 1.98 1.59 2.68 0.42 0.04 0.45 0.70 0.28 1.76 4.26 0.06 6.80 003 0.80 11.42 2-75 3.83 1. 00 7.86 1399 19.00 258 HUMAN FOODS AND THEIR NUTRITIVE VALUE Family No. 2 Protein Fat Carbohydrates Lb. Lb. Lb. 15 lb. flour 1.89 0.12 II. 15 5 lb. skim milk ... 0.16 0.0 1 0.26 10 lb. round steak I.81 1.26 — 10 lb. beef . 1.32 2.02 — 5 lb. cheese . ... 1.40 1-75 — 5 lb. oatmeal . . . . 0.78 0.36 340 6 lb. butter 0.03 5.10 — 3 lb. shortening ... — 2.55 — 3 lb. prunes 0.03 — 0.60 25 lb. apples ... . . 0.12 — 2.50 25 lb. potatoes . . . 0.45 0.03 3-83 40 lb. milk .... . . 1.44 1.60 1.90 5 lb. beans . . . 1. 12 — 3.00 10.55 14.80 26.64 Difference in nutrients in favor of family No. 2, consuming the 2.69 0.81 7.64 cheaper combination of foods 255. Food in its Relation to Mental and Physical Vigor. — When the body is not properly supplied with food, the best results in the form of productive work cannot be secured. There is a close relationship between the nature of the food consumed and mental activity, also ability to satisfactorily perform physical labor. " The productive power of the individual as well as of the nation depends doubtless upon many factors other than food, such as race, climate, habit, etc.. DIETARY STUDIES 259 but there is no gainsaying the fact that diet has also a profound and direct influence upon it."^^ If the body is diseased, it cannot make the right uses of the food, and often the food is blamed when the trouble is due primarily to other causes. The fact that a diseased digestive tract is unable to utilize some foods is no valid reason why these foods should be discarded in the dietary of persons in normal health, particularly when the food is in no way responsible for the disease. Some diseases are most prevalent in the case of a restricted diet. A change in the dietary of the Japa- nese navy greatly improved the health of the sailors. " The prevalence of kakke or beriberi in the navy turned the atten- tion of many medical specialists toward the problem of nutrition. . . . It was generally believed that there was some very close connection between the disease and the rice diet. . . . One outcome of these investigations was the passage of the food supply act of the navy in 1884. The ration provided in accordance with this act was sufficient to furnish an abundance of protein and energy. . . . Fol- lowing the change of ration in 1884, the prevalence of the disease was very materially diminished, and at the end of three years cases of kakke were practically unknown among the marines." *^ 256. Dietary Studies in Public Institutions. — Dietary studies in public institutions, as prisons, and asylums for the insane, show that it is possible to secure greater variety of food containing a larger amount of nutrients, and even at a reduction in cost.^ In such institutions it is important that the food should be not only ample 26o HUMAN POODS AND THEIR NUTRITIVE VALUE in amount, but wholesome and nutritious, as many of the inmates respond both physically and mentally to an improved diet. For humanitarian as well as eco- nomic reasons institutional dietetics should more gener- ally be placed under the supervision of skilled dietists. CHAPTER XVIII RATIONAL FEEDING OF MAN 257. Object. — Rational feeding of man has for its object the regulation of the food supply in accord with the demands of the body. It is based upon the same principles as the rational feeding of animals ; in each, the best results in the way of health, amount of labor performed, and economy are secured when the body receives nutrients sufficient for the production of heat and energy and for the repair of worn-out tissues. Ra- tional feeding is simply regulation of the food, both as to kind and amount, to meet the needs of the body.''^^ 258. Standard Rations. — In human feeding, as in animal feeding, it is not possible to lay down hard and fast rules as to the quantity of nutrients required for a standard ration.*^ As stated in the chapter on Die- tary Studies, such standards have been proposed, but they are to be considered as tentative rather than abso- lute, for the amount of food required by different persons must necessarily vary with the individuality. While it is impossible to estabhsh absolute standards, any large variation from the provisional standards usually 261 262 HUMAN FOODS AND THEIR NUTRITIVE VALUE results in lessened ability to accomplish work, ill health, or increased expense. 259. Amounts of Food Consumed. — The approximate amounts of some food articles consumed per day are as follows : Range Approximate Amount in Lbs. Bread . 6 to 14 OZ. 0.50 Butter . 2 to 5 OZ. 0.12 Potatoes 8 to 16 OZ. 0.75 Cheese . . . . I to 4 OZ. 0.12 Beans ... . . I to 4 OZ. 0.12 Milk . .... 8 to 32 OZ. — Sugar . . . 2 to 5 oz. 0.20 Meats . . . . . 4 to 12 OZ. 0.25 Oatmeal 1 to 4 OZ. 0.12 In the calculation of rations it is desirable that the amount of any food article should not exceed that des- ignated, unless for some special reason it has been found the food can consistently be increased. The amount of nutrients given in dietary standards is for one day, and the nutrients may be divided among the three meals as desired. It is to be noted that, or- dinarily, the foods which supply carbohydrates are flour, corn meal, cereal products, potatoes, beans, sugar, and milk ; those which supply fat are milk, butter, lard, and meats; and those which supply protein in RATIONAL FEEDING OF MAN 263 liberal amounts are beans, cheese, meats, oatmeal, cereals, bread, and milk. 260. Average Composition of Foods. — The amounts of nutrients in foods are determined from the average composition of the foods. These figures for average composition are, based upon analyses of a large number of samples of food materials." In individual cases it will be found that foods may vary from the standards given; as for example, milk may contain from 2.5 to S per cent of fat, while the protein and fat of meats vary appreciably from the figures given for average compo- sition. With the cereals and vegetable foods, variations from the standards are small. In the table, the com- position of the food as purchased represents all of the nutrients in the food, including those in the refuse, trimmings, or waste, while the figures for the edible por- tion represent the nutrients in the food after deducting what is lost as refuse. In making calculations, the student should use the figures given for the foods as -purchased, unless the weights are of the edible portion only. The figures in the table are on the basis of per- centage amounts, or nutrients in 100 pounds of food. By moving the decimal point two places to the left, the figures will represent the nutrients in one pound, and if this is multipHed by the number of pounds or fraction of a pound used, the quantity of nutrients is secured. For example, suppose bread contains 9.5 per cent of protein and 56 per cent of carbohydrates, i pound 264 HUMAN FOODS AND THEIR NUTRITIVE VALUE would contain 0.095 pound of protein, 0.56 pound of carbohydrates; and 0.5 of a pound would contain approximately 0.05 pound of protein and 0.28 pound of carbohydrates. In calculating rations, it is not necessary to carry the figures to the third decimal place. Fig. 60. — Food Articles for a Human Ration. 261. Example of a Ration. — Suppose it is desired to calculate a ration for a man at light muscular work. First, note the requirements in the way of nutrients in the table " Dietary Standards," Section 246. Such a ration should supply approximately 0.22 pound each of protein and fat, and 0.77 pound of carbohydrates, and should yield 2800 calories. A trial ration is made by combining the following : RATIONAL FEEDING OF MAN 265 Bread Butter Potatoes Milk . Sugar Beef . Ham . Oatmeal Eggs • Pound 0.50 0.12 0.75 I. GO 0.12 0.25 0.20 0.12 0.25 The quantities of nutrients in these food materials are approximately as follows : Ration for Man at Moderate Work Lb. Protein Lb. Bread . . Butter . . . Potato . . . Milk . . . Sugar . . . Beef (round) Ham . . . Oatmeal . . Eggs . . . Squash . 0.50 0.12 0.75 1. 00 0.12 0.25 0.20 0.12 0.25 0.20 Fat Lb. 0.05 O.OI 0.04 0.05 0,03 0.02 0.03 0.23 O.OI O.IO 0.04 0.03 0.07 O.OI 0.03 0.29 C.H. Lb. 0.29 0.12 0.05 0.08 0.67 Calories 653 432 244 323 ' 192 218 331 223 164 25 2805 It is to be noted that this ration contains approxi- mately the amount of protein called for in the standard 266 HUMAN FOODS AND THEIR NUTRITIVE VALUE ration, while the fat is slightly more and the carbohy- drates are less. The food value of the ration is prac- tically that called for in the standard. This ration is sufficiently near the standard to supply the nutrient requirements of a man at light muscular work. To supply palatability, some fruit and vegetables should be added to the ration. These will contribute but little to the nutrient content, but are necessary in order to secure health and the best returns from the other foods, and as previously stated, they are not to be estimated entirely upon the basis of nutrient content. A number of food articles could be substituted in this ration, if desired, either in the interests of economy, palatability, or personal preference. 262. Requisites of a Balanced Ration. — Reasonable combinations of foods should be made to form balanced rations.^ A number of foods slow of digestion, or which require a large amount of intestinal work, should not be combined ; neither should foods which are easily digested and which leave but httle indigestible residue. After a ration has been calculated and found to contain the requisite amount of nutrients, it should be critically examined to see whether or not it fulfills the following requirements : 1 . Economy and adaptability to the work required. 2. Necessary bulk or volume. 3. Desired physiological influence of the foods upon the digestive tract, whether constipating or laxative in character. 4. Ease of digestion. RATIONAL FEEDING OF MAN 267 J. Effect upon health. It is recognized that there are foods wholesome and nutritious, that cannot be used by some per- sons, while with others the same foods can be consumed with impunity. As explained in the chapter on Dietary Studies, the nutrients should be supplied from a number of foods rather than from a few, because it is believed the various nutrients, particularly the proteins, are not absolutely identical from all sources, or equal in nutritive value. EXAMPLES 1. Calculate a ration for a man with little physical exercise. 2. Calculate a ration for a man at hard muscular labor, and give the approximate cost of the ration. 3. Calculate the amounts of food and the nutrient requirements for a family of seven for 10 days ; five of the family to con- sume 0.8 as much as an adult. Calculate the cost of the food ; then calculate on the same basis the probable cost of food for one year, adding 20 per cent for fluctuation in market price and additional foods not included in the list. 4. Weigh out the food articles used in problem No. 2, and appor- tion them among three meals. CHAPTER XIX WATER 263. Importance. — Water is one of the most essential food materials. It enters into the composition of the body, and without it the nutrients of foods would be unavailable, and life could not be sustained. Water unites chemically with various elements to form plant tissue and supplies hydrogen and oxygen for the produc- tion of organic compounds within the leaves of plants. In the animal economy it is not definitely known whether or not water furnishes any of the elements of which the tissues are composed, as the food contains liberal amounts of hydrogen and oxygen ; it is necessary mainly as the vehicle for distributing nutrients in sus- pension and solution, and as a medium in which chemical, physical, and physiological changes essential to life processes take place. From a sanitary point of view, the condition of the water supply is of great importance, as impure water seriously affects the health of the con- sumer.^'^ 264. Impurities in Water. — Waters are impure be- cause of: (i) excessive amounts of alkaline salts and other mineral compounds ; (2) decaying animal and 268 WATER 269 vegetable matters which act chemically as poisons and irritants, and which may serve as food for the develop- ment of objectionable bacterial bodies; and (3) injurious Fig. 61. — Dirt and Impurities in a Surface Well Water. bacteria. The most common forms of impurities are excess of organic matter and bacterial contamination. The sanitary condition of water is greatly influenced by the character of the soil through which it flows and the extent to which it has been polluted by surface drain- 270 HUMAN FOODS AND THEIR NUTRITIVE VALUE 265. Mineral Impurities. — The mineral impurities of water are mainly soluble alkaline and similar compounds dissolved by the water in passing through various layers of soil and rock. When water contains a large amount of sodium chloride, sodium sulphate or carbonate, or other alkaline salts, it is termed an " alkali water." Where water passes through soil that has been largely formed from the decay of rocks containing alkaline minerals, the water dissolves some of these minerals and becomes alkaline. The kind of alkali determines the character of the water ; in some cases it is sodium car- bonate, which is particularly objectionable. The con- tinued use of strong alkali water causes digestion dis- orders, because of the irritating action upon the digestive tract. Hard waters are due' to the presence of lime compounds. In regions where limestone predominates, the carbon dioxid in water acts as a solvent, producing hard waters. Waters that are hard on account of the presence of calcium carbonate give a deposit when boiled, due to hberation of the carbon dioxid which is the material that renders the lime soluble. Calcium sulphate, or gypsum, on the other hand, imparts per- manent hardness. There is no deposit when such waters are boiled. A large number of minerals are found in various waters, often sufficient in amount to impart physiological properties. Water that is highly charged with mineral matter is difficult to improve sufficiently for household purposes. About the only way is by distillation.^^ WATER 271 266. Organic Impurities. — Water that flows over the surface of the ground comes in contact with animal and vegetable material in various stages of decay, and as a result some is dissolved and some is mechanically carried along by the water. After becoming soluble, the organic matter undergoes further chemical changes, as oxidation and nitrification caused by bacteria. If the organic matter contain a large amount of nitrogenous material, particularly of proteid origin, a series of chemical changes induced by bacterial action takes place, resulting in the production of nitrites. The nitrifying organisms first produce nitrous acid products (nitrites), and in the further development of the nitrifying process these are changed to nitrates. The ammonia formed as the result of the decomposition of nitrogenous organic matterreadily undergoes nitrification changes. Nitrates and nitrites alone are not injurious in water, but they are usually associated with objectionable bacteria and generally indicate previous contamination.* 267. Interpretation of a Water Analysis. — " Total solid matter" represents all the mineral, vegetable, and animal matter which a water contains. It is the residue obtained by evaporating the water to dryness at a tem- perature of 212° F. Average drinking water contains from 20 to 90 grains per gallon of soHd matter. " Free ammonia" is that formed as a result of the decomposi- tion of animal or vegetable matter containing nitrogen. Water of high purity usually contains less than 0.07 272 HUMAN FOODS AND THEIR NUTRITIVE VALUE parts per million of free ammonia. " Albuminoid am- monia " is derived from the partially decomposed ani- mal or vegetable material in water. The greater the amount of nitrogenous organic impurities, the higher the albuminoid ammonia. A good drinking water ought not to contain more than o. 10 part per million of albu- minoid ammonia. An abnormal quantity of chlorine indicates surface drainage or sewage contamination, or an excess of alkaline matter, as common salt. Nitrites should not be present, as they are generally associated with matter not completely oxidized. Nitrites are usu- ally considered more objectionable than nitrates; both are innocuous unless associated with disease-producing nitroorganisms. 268. Natural Purification of Water. — River waters are sometimes dark colored because of large amounts of dissolved organic matter, but in contact with the sun and air they gradually undergo natural purification and the organic matter is oxidized. However, absolute reli- ance cannot be placed upon natural purification of a bad water, as the objectionable organisms often have great resistive power. There is no perfectly pure water except that prepared in the chemical laboratory by dis- tillation. All natural waters come in contact with the soil and air, and necessarily contain impurities propor- tional to the extent of their contamination. 269. Water in Relation to Health. — There are many diseases, of which typhoid fever is a type, that are dis- WATER 273 tinctly water-born. The typhoid bacilli, present in count- less numbers in the feces of persons suffering or con- valescent from typhoid fever, find their way into streams, lakes, and wells.^^ They retain their vitality, and when they enter the digestive tract of an individual, rapidly increase in numbers. Numerous disastrous outbreaks of typhoid fever have been traced to contamination of water. Coupled with the sanitary improvement of a city's water supply, there is diminution of typhoid fever cases, and a noticeable lowering of the death rate. Many cities and villages are dependent for their water upon rivers and lakes into which surface drainage finds its way, with all contaminating substances. Mechanical sedimentation and filtration greatly improve waters of this class, but do not necessarily render them entirely pure. Compounds of iron and aluminium are sometimes added in small amounts, under chemical supervision, to such waters to precipitate the organic impurities. Spring waters are not entirely above suspicion, as often- times the soil through which they flow is highly polluted. All water of doubtful purity should be boiled, and there are but few natural waters of undoubted purity. There is no such thing as absolutely pure water in a state of nature. The mountain streams perhaps approach near- est to it where there are no humans to pollute the banks ; but then there are always the beasts and birds, and they, too, are subject to disease. There are very few waters that at some time of the year and under some conditions are not contaminated with disease-producing organisms. 274 HUMAN FOODS AND THEIR NUTRITIVE VALUE No matter how carefully guarded are the banks of lakes furnishing the water supply of cities, more or less ob- jectionable matter will get in. In seasons of heavy rains, large amounts of surface water enter the lakes, carrying along the filth gathered from many acres of land drained by the streams entering the lakes. Some of the most serious outbreaks of typhoid fever have come from temporary contamination of ordinarily fairly good drink- ing water. In general, too little attention is given to the purity of drinking water. It is just as important that water should be boiled as that food should be cooked. One of the objects of cooking is to destroy the injurious bacteria, and they are frequently more numerous in the drinking water than in the food. The argument is sometimes advanced that the min- eral matter present in water is needed for the construc- tion of the bone and other tissues of the body, and that distilled water fails to supply the necessary mineral matter. This is an erroneous assumption, as the min- eral matter in the food is more than sufficient for this purpose. When water is highly charged with mineral salts, additional work for their elimination is called for on the part of the organs of excretion, particularly the kidneys; and furthermore, water nearly saturated with minerals cannot exert its full solvent action. In discussing the immediate benefits resulting from improvement of water, Fuertes says : ^^ " Immediately after the change to the ' four mile intake ' at Chi- cago in 1893, there was a great reduction in typhoid. Lawrence, ■ WATER 275 Mass., showed a great improvement with the setting of the filters in operation in September, 1893 ; fully half of the deaths in 1894 were among persons known to have used the unfiltered canal water. The conclusion is warranted that for the efficient control of the death rate from typhoid fever it is necessary to have efficient sewer- age and drainage, proper methods of living, and pure water. The reason why our large cities, which are all provided with sewerage, have such high death rates is therefore without doubt their continu- ance of the filthy practice of supplying drinking water which carries in solution and suspension the washings from farms, from the streets, from privies, from pigpens, and the sewage of cities. . . . And also we should recognize the importance of flies and other winged insects and birds which feed on offal as carriers of bacteria of specific diseases from points of infection to the watersheds, and the consequent washing of newly infected matter into our drinking water by rains." There is a very close relationship between the sur- face water and that of shallow wells. A shallow well is simply a reservoir for surface water accumulations. It is stated that, when an improved system of drainage was introduced into a part of London, many of the shallow wells became dry, indicating the source from which they received their supply. Direct subterranean connection between cesspools and wells is often traced in the following way: A small amount of lithium, which gives a distinct flame reaction, and a minute trace of which can be detected with the spectroscope, is placed in the cesspool, and after a short time a lithium reaction is secured from the well water. Rain water is relied upon in some localities for drink- ing purposes. That collected in cities and in the vicin- 276 HUMAN FOODS AND THEIR NUTRITIVE VALUE ity of barns and dwellings contains appreciable amounts of organic impurities. The brown color is due to the impurities, ammonium carbonate being one of these. There are also traces of nitrates and nitrites obtained from the air. When used for drinking, rain water should be boiled. 270. Improvement of Waters. — Waters are improved by: (i) boiling, which destroys the disease-producing organisms ; (2) filtration, which removes the materials mechanically suspended in the water ; and (3) distilla- tion, which eliminates the impurities in suspension and solution, as well as destroys all germ life. 271. Boiling Water. — In order to destroy the bac- teria that may be in drinking water, it is not sufficient to heat the water or merely let it come to a boil. It has been found that if water is only partially sterilized and then cooled in the open air, the bacteria develop more rapidly than if the water had not been heated at all. It should boil vigorously five to ten minutes ; cholera and typhoid bacteria succumb in five minutes' or less. Care should be taken in cooling that the water is not exposed to dust particles from the air nor placed in open vessels in a dirty refrigerator. It should be kept in perfectly clean, tight-stoppered bottles. These bottles should be frequently scalded. Great reliance may be placed upon this method of water purification when properly carried out. WATER 277 272. Filtration. — Among the most efficient forms of water filters are the Berkefeld and Pasteur. The Pas- teur filter is made of unglazed porcelain, and the Berkefeld of fine infusorial earth (finely divided SiOg). Both are por- ous and allow a moderately rapid flow of water. The flow from the Berkefeld fil- ter is more rapid than from the Pasteur. The mechani- cal impurities of the water are deposited upon the filter- ing surface, due to the attrac- tion which the material has for particles in suspension. These particles usually are the sources of contamination and carry bacteria. When first used, filters are satisfac- tory, but unless carefully looked after they soon lose their ability to remove germs from the water and may increase the impurity by accumulation. Small faucet filters are made of porous stone, asbestos, charcoal, etc. Many of them are of no value whatever or are even worse than valueless. Filters should be frequently cleansed in boiling water or in steam under pressure. Unless this is done, the filters may become incubators for bacteria. Fig. 62. -Pasteur Water Filters. 278 HUMAN FOODS AND THEIR NUTRITIVE VALUE 273. Distillation. — When an unquestionably pure water supply is desired, distillation should be resorted to. There are many forms of stills for domestic use which are easily manipulated and produce distilled water economically.^^ The mineral matter of water is Fig. 63.— Vv'ater Still. in no way essential for any functional purpose, and hence its removal through distillation is not detrimental. 274. Chemical Purification. — Purification of water by the use of chemicals should not be attempted in the household or by inexperienced persons. When done under supervision of a chemist or bacteriologist, it may be of great value to a community. Turneaure and WATER 279 Russell,^* in discussing the purification of water by addition of chemicals, state : " There are a considerable number of chemical substances that may- be added to water in order to purify it by carrying down the sus- pended matter as well as bacteria, by sedimentation. Such a pro- cess of purification is to be seen in the addition of alum, sulphate of iron, and calcium hydrate to water. Methods of this character are directly dependent upon the flocculating action of the chemical added, and the removal of the bacteria is accomplished by subsid- ence." 275. Ice, — The purity of the ice supply is also of much importance. While freezing reduces the number of organisms and lessens their vitality, it does not make an impure water absolutely wholesome. The way, too, in which ice is often handled and stored subjects it to contamination, and foods which are placed in direct contact with it mechanically absorb the impurities which it contains. For cooUng water, ice should be placed around rather than in it. Diseases have frequently been traced to impure ice. The only absolutely pure ice is that made from distilled water. 276. Mineral Waters. — When water is charged with carbonic acid gas under pressure, carbonated water re- sults, and when minerals, as salts of sodium, potassium, or lithium, are added, artificial mineral waters are pro- duced. Natural mineral waters are placed on the market to some extent, but most mineral waters are artificial products and they are sometimes prepared from water of low sanitary character. Mineral waters 28o HUMAN FOODS AND THEIR NUTRITIVE VALUE should not be used extensively except under medical direction, as many have pronounced medicinal proper- ties. Some of the constituents are bicarbonates of so- dium, potassium, and lithium ; sulphates of magnesium (Epsom salts) and calcium; and chloride of sodium. The sweetened mineral waters, as lemonade, orangeade, ginger ale, and beer, contain sugar and organic acids, as citric and tartaric, and are flavored with natural or arti- ficial products. Most of them are prepared without either fruit or ginger. Natural mineral waters used under the direction of a physician are often beneficial in cases of chronic digestion disorders or other diseases. 277. Materials for Softening Water. — The materials most commonly used for softening water are sodium carbonate (washing soda), borax, ammonia, ammonium carbonate, potash, and soda lye. Waters that are very hard with limestone should have a small amount of washing soda added to them. Two ounces for a large tub of water is the most that should be used, and it should first be dissolved in a little water. If too much soda is used, it is injurious, as only a certain amount can be utilized for softening the water, and the excess simply injures the hands and fabric. When hard limewater is boiled and a very little soda lye added, a precipitate of carbonate of Hme is formed, and then if the water is strained, it is greatly improved for washing purposes. Borax is valuable for making some hard waters soft. It is not as strong in its action as is sodium carbonate. WATER 281 For the hardest water ^ pound of borax to a large tub- ful may be used ; most waters, however, do not need so much. Ammonia is one of the most useful reagents for softening water. It is better than washing soda and borax, because the ammonia is volatile and does not leave any residue to act on the clothes, thus causing injury. For bathing purposes, the water should be softened with ammonia, in preference to any other material. Ammonia should not be poured directly into hot water ; it should be added to the water while cold, or to a small quantity of cold water, and then to the warm water, as this prevents the ammonia from vapor- izing too readily. Ammonia produces the same effect as potash or soda lye, without leaving a residue in the garments washed. It is especially valuable in washing woolen goods or materials liable to shrink. Waters which are hard with alum salts are greatly benefited by the addition of ammonia. A little in such a water will cause a precipitate to form, and when the water is strained it is in good condition for cleaning purposes. Ammonium carbonate is used to some extent as a soft- ening and cleaning agent, and is valuable, as there is no injurious effect upon clothing, because it readily volatil- izes. Caustic potash and caustic soda are sometimes employed for softening water, but they are very active and are not adapted to washing colored or delicate fabrics. They may be used for very heavy and coarse articles that are greasy, — not more than a gram in a gallon of water. Bleaching powder is not generally a 282 HUMAN FOODS AND THEIR NUTRITIVE VALUE safe material for cleansing purposes, as it weakens the texture of clothing. After a contagious disease, articles may be soaked in water containing a little bleaching powder and a few drops of carbolic acid, followed by thorough rinsing and bleaching in the sun. But as a rule formaline is preferable for disinfecting clothing. It caij be used at the rate of about one pound to 100 gallons of water. Bleaching powder, caustic potash or soda, and strong soap are not suitable for cleaning woodwork, because of the action of the alkali on paint and wood ; they roughen the surface and discolor the paint. Waters vary so in composition, that a material suitable for softening one may not prove to be the best for softening another. The special kind must be de- termined largely by trial, and it should be the aim to use as little as possible. When carbolic acid, formaline, bleaching powder, and caustic soda are used, the hands should be protected and the clothes should be well rinsed. 278. Economic Value of a Pure Water Supply. — From a financial point of view, the money spent in securing pure water is one of the Fig. 64.— Typhoid best investments a community can make. Statisticians estimate the death of an adult results in a loss to the state of from ^1000 to $5000; and to the losses sustained by death must be added those incurred by sickness and by less- WATER 283 ened quality and quantity of work through impaired vitality, — all caused by using poor drinking water. Wherever plants have been installed for improving the sanitary condition of the water supply, the death rate has been lowered and the returns to the community have been far greater than the cost of the plant. Im- pure water is the most expensive food that can be consumed. CHAPTER XX FOOD AS AFFECTED BY HOUSEHOLD SANITATION AND STORAGE 279. Injurious Compounds in Foods. — An ordinary chemical analysis of a food determines only the nutri- ents, as protein, carbohydrates, and fats ; and unless there is reason to beUeve the food contains injurious substances no special tests for these are made. There are a number of poisonous compounds that foods may contain, and many of them can but imperfectly be determined by chemical analysis. Numerous organic compounds are produced in foods as the result of the workings of microorganisms ; some of these are poison- ous, while others impart only special characteristics, as taste and odor. The poisonous bacteria finding their way into food produce organic compounds of a toxic character ; and hence it is that the sanitary condition of a food, as influenced by preparation and storage, is often of more vital importance than the nutrient content. ^^ 280. Sources of Contamination of Food. — As a rule, too little attention is given to the sanitary handhng and preparation of foods. They are often exposed to impure 284 FOOD AS AFFECTED BY SANITATION AND STORAGE 285 air and to the dust and filth from unclean streets and surroundings, and as a result they become inoculated with bacteria, which are often the disease-producing kind. Gelatine plates exposed by bacteriologists under the same conditions as foods develop large numbers of FIG. 65. —Tuberculosis Bacilli. (After Conn.) Often present in dust particles and contaminated foods. injurious microorganisms. In order to avoid contami- nation in the handling of food, there must be: (i) pro- tection from impure air and dust; (2) storage in clean, sanitary, and ventilated storerooms and warehouses ; (3) storage of perishable foods at a low temperature so as to retard fermentation changes ; and (4) workmen free from contagious diseases in all occupations pertaining 286 HUMAN FOODS AND THEIR NUTRITIVE VALUE to the preparation of foods. Ordinarily, foods should not be stored in the paper wrappers in which they are purchased, as unclean paper is often a source of contamination. 281. Sanitary Inspection of Food. — During recent years some state and city boards of health have in- troduced sanitary inspection of foods, with a view of preventing contamination during manufacture and transportation, and this has done much to improve the quality and wholesomeness. Putrid meats, fish, and vegetables are not allowed to be sold, and foods are required to be handled and stored in a sanitary way. Next to a pure water supply, there is no factor that so greatly influences for good the health of a community as the sanitary condition of the food. While the cook- ing of foods destroys many organisms, it often fails to render innocuous the poisons which they produce, and furthermore the unsound foods when cooked are not en- tirely wholesome, and they have poor keeping qualities. Often meats, vegetables, and other foods eaten un- cooked, as well as the numerous cooked foods, are exposed in dirty market places, and accumulate large amounts of filth, and are inoculated with disease germs by flies. Protection of food from flies is a matter of vital importance, as they are carriers of many diseases. In the case of typhoid fever, next to impure drinking water flies are credited with being the greatest dis- tributors of the disease germs. ^ FOOD AS AFFECTED BY SANITATION AND STORAGE 287 282. Infection from Impure Air. — The dust particles of the air contain decayed animal and vegetable matter in which bacteria are present ; these find their way into the food when it is not carefully protected, into the water supply, and also into the lungs and other organs Fig. 66. — Diphtheria Bacilli. (After Conn.) Often present in dust particles and in food unprotected from dust. of the body. When foods are protected from the me- chanical impurities which gain access through the air, and fermentation is delayed by storage at a low tem- perature, digestion disorders are greatly lessened. From a sanitary point of view, the air of food storerooms and of living rooms should be of equally high purity. When foods are kept in unventilated living rooms, they become 288 HUMAN FOODS AND THEIR NUTRITIVE VALUE contaminated with the impurities thrown off from the lungs in respiration, which include not only carbon di- oxid, but the more objectionable toxic organic materials. Vegetable foods need to be stored in well-ventilated places, as the plant cells are still alive and carrying on hfe functions, as the giving off of carbon dioxid, which is akin to animal respiration ; in fact, it is plant-cell respiration. Provision should be made for the removal of the carbon dioxid and other products, as they con- taminate the air. When vegetable tissue ceases to pro- duce carbon dioxid, death and decay set in, accompanied by fermentation changes. 283. Storage of Food in Cellars. — Cellars are often in a very unsanitary condition, damp, poorly lighted, un- ventilated, and the air filled with floating particles from decaying vegetables. The walls and shelves absorb the dust and germs from the foul air and are bacterially con- taminated, and whenever a sound food is stored in such a cellar, it readily becomes inoculated with bacteria. There is a much closer relationship existing between the atmosphere of the cellar and that of the house than is generally realized. An unclean cellar means contami- nated air throughout the house. When careful attention is given to the sanitary condition of the cellar, many of the more common diseases are greatly reduced. Cases of rheumatism have often been traced to a damp cellar. In some localities where the cellars are unusually un- sanitary, there is in the season of spring rains, when FOOD AS AFFECTED BY SANITATION AND STORAGE 289 they are especially damp and contain the maximum of decayed vegetation, a prevalence of what might be called "cellaritis." The symp- toms differ and the trouble is variously at- tributed, but the real cause is the same, al- though overlooked, for, unfortunately, doctors do not visit the cellar. Cellars should be frequently cleaned and disinfected, .using for the purpose some of the well-known disin- fectants, as formaline, bleaching powder, or a dilute solution of car- balic acid. It has been •found in large cities, when the spread of such diseases as yellow fever was imminent, that a general and thorough cleaning up of streets and cellars with the improved sanitary conditions resulting greatly lowered the usual death rate. Fig. 67. — DiiNc Fungus. (After BUTTEKS.) Often present on surface of unclean vegetables. 284. Sunlight, Pure Water, and Pure Air as Disin- fectants. , — The most effectual and valuable disinfectants 290 HUMAN FOODS AND THEIR NUTRITIVE VALUE are sunlight, pure water, and pure air. Many kinds of microorganisms, particularly those that are disease-pro- ducing, are destroyed when exposed for a time to sun- light. The chemical action of the sun's rays is destructive to the organic material which makes up the composition of many of these organisms, while higher forms of or- ganic life are stirred into activity by it. The disinfecting power of sunlight should be made use of to the fullest extent, not only in the house, but plenty of sunlight should also be planned for in constructing barns and other buildings where milk- and meat-producing animals are kept. Pure water is also a disinfectant, but when water becomes polluted it loses this power. Many dis- ease-producing organisms are rendered inactive when placed in pure water. Water contains more dissolved oxygen than air, and apparently a portion of the oxygen in water is in a more active condition than that in air. Pure air, too, is a disinfectant ; the ozone and hydrogen peroxide and oxides of nitrogen, which are present in traces, exert a beneficial influence in oxidizing organic matter. Fresh air and sunlight, acting jointly, are na- ture's most effectual disinfectants. Sunshine, fresh air, and pure water are a health-producing trinity. In dis- cussing the importance of pure air, water, and sunlight, Ellen H. Richards ^'^ says : ''The country dweller surrounds his house with evergreens or shade trees, the city dweller is surrounded with high brick walls. Blinds, shades, or thick draperies shut out still more, and prevent the bene- ficial sunlight from acting its role of germ prevention and germ FOOD AS AFFECTED BY SANITATION AND STORAGE 29I destruction. Bright-colored carpets and pale-faced children are the opposite results which follow. Sunlight, pure air, and pure water are our common birthright which we often bargain away for so-called comforts.'' And Dr. Woods Hutchinson says of sunlight : " It is a splendid and matchless servant in the promoting of healthfulness of the house, for which no substitute has yet been dis- covered. It is the foe alike of bacilli and the blues ; the best tonic ever yet invented for the liver and for the scalp, and for everything between, the only real complexion restorer, and the deadliest foe of dirt and disease." 285. Utensils for Storage of Food. — In order that dishes and household utensils may be kept in the best sanitary condition, they should be free from seams, cracks, and crevices where ■ dust and dirt particles can find lodgment. From the seams of a milk pail that has not been well washed, decaying milk solids can be removed with the aid of a pin or a toothpick. This material acts as a " starter " or culture when pure, fresh milk is placed in the pail, contaminating it and causing it to become sour. Not only is this true of milk, but also of other foods. Wooden utensils are not satisfactory for the Fig. 68. — Dirt and manure em- bedded IN Surface of Celery. 292 HUMAN FOODS AND THEIR NUTRITIVE VALUE handling, storage, or preparation of foods, as it is diffi- cult to keep wood in a sanitary condition. Uncleanliness of dishes in which foods are placed is too often caused by the use of foul dishcloths and failure to thoroughly wash and rinse the dishes. It is always well to rinse dishes with scalding water, as colds and skin diseases may be communicated from the edges of drinking glasses, and from forks and spoons, and, unless the dish towels are kept scrupulously clean, it is more sanitary to drain the dishes than to wipe them. 286. Contamination from Unclean Dishcloths. — When the dishcloth is foul, the fat absorbed by the fibers be- comes rancid, the proteids undergo putrefaction changes with formation of ill-smelling gases containing nitrogen, the carbohydrates ferment and are particularly attractive to flies, and all the various disease germs collected on the surface of the dishcloth are, along with the rancid fat and other putrifying materials, distributed over the sur- face of the dishes with which the cloth comes in contact. 287. Refrigeration. — At a low temperature the in- soluble or unorganized ferments become inactive, but the chemical ferments or enzymes are still capable of carrying on fermentation. Thus it is that a food, when placed in a refrigerator or in cold storage, continues to undergo chemical change. An example of such enzymic action is the curing of beef and cheese in cold storage. A small amount of ventilation is required when foods are refrigerated, just sufficient to keep up a slight circulation FOOD AS AFFECTED BY SANITATION AND STORAGE 293 of air. It seems not to be generally understood that all fermentation changes do not cease when food is placed in refrigerators, and this often leads to neglect in their care. , Cleanliness is equally as essential, or more so, in the refrigeration of food as in its handling in other ways. Fig. ,69. — Contamination of Well Water from Surface Drainage. (After Farmers' Bulletin, U. S. Dept. Agr.) Too often the refrigerator is neglected, milk and other food is spilt, filling the cracks, and slow decomposition sets in. A well-cared-for refrigerator is an important factor in the preservation of food, but when it is neg- lected, it becomes a source of contamination. Unclean vegetables and food receptacles, impure ice and foul air, are the most common forms of contamination. The 294 HUMAN FOODS AND THEIR NUTRITIVE VALUE chemical changes which foods undergo during refriger- ation are such as result in softening of the tissues. 288. Soil. — The soil about dwellings and places where foods are stored frequently becomes polluted with de- caying animal and vegetable matter, and in such soils disease-producing organisms readily find lodgment. Poorly drained soils containing an excess of vegetable matter furnish a medium in which the tapeworm and the germs of typhoid fever, lockjaw, and various diseases affecting the digestive tract, may propagate. The wind carries the dust particles from these contaminated places into unprotected food, where they cause fer- mentation changes and the disease germs multiply. In considering the sanitary condition of a locality, the character of the soil is an important factor. When- ever there is reason to suspect that a soil is unsanitary, it should be disinfected with lime or formaldehyde. Soils about dwellings need care and frequent disinfecting to keep them in a sanitary condition, equally as much as do the rooms in the dwellings.^ In the growing of garden vegetables, frequently large quantities of ferti- lizers of unsanitary character are used, and vegetables often retain mechanically on their surfaces particles of these. To this dirt clinging to the vegetables have been traced diseases, as typhoid fever and various digestion disorders. 289. Disposal of Kitchen Refuse. — Refuse, as vege- table parings, bones, and meat scraps, unless they are FOOD AS AFFECTED BY SANITATION AND STORAGE 295 used for food for animals or collected as garbage, should preferably be burned ; then there is no danger of their furnishing propagating media for disease germs. Gar- bage cans should be kept clean, and well covered to protect the contents from flies. Where the refuse cannot be burned, it should be composted. For this, a well- drained place should be selected, and the refuse should be kept covered with earth to keep off the flies and absorb the odors that arise from the fermenting material, and to prevent its being carried away by the wind. Lime should be sprinkled about the compost heap, and from time to time it should be drawn away and the place covered with clean earth. It is very unsanitary to throw all of the kitchen refuse in the same place year after year without resorting to any means for keeping the soil in a sanitary condition. Although composting refuse is not as sanitary as burning, it is far more sani- tary than neglecting to care for it at all, as is too fre- quently the case. Ground polluted with kitchen refuse containing large amounts of fatty material and soap becomes diseased, so that the natural fermentation changes fail to take place, and the soil becomes " sewage sick " and gets in such a condition that vegetation will not grow. Failure to properly dispose of kitchen refuse is frequently the cause of the spread of germ diseases, through the dust and flies that are attracted by the material and carry the germs from the refuse pile to food. Where there is no drainage system, disposal of the 296 HUMAN FOODS AND THEIR NUTRITIVE VALUK liquid refuse is a serious problem. Drain basins and cesspools are often resorted to, and these may become additional sources of contamination. As stated in the chapter on well water, direct communication is frequently estabhshed between such places and shallow wells. Fig. 70. — Plumbi.n.'g of Sink. I, I, house side of trap, filled with water; 2, vent pipe; 3, drain pipe connect- ing w ith sewer. Where the only place for the disposal of waste water is the surface of the ground, it should be thrown some dis- tance from the house and where it will drain from and not toward the well. The land should be well drained and open to the sunlight. Coarse sand and Hme should be sprinkled over it frequently, and occasionally the soil should be removed and replaced with fresh. Sunlight, aeration, and disinfection of the soil and good drainage FOOD AS AFFECTED BY SANITATION AND STORAGE 297 are necessary, in order to keep in a sanitary condition the place where the dish water is thrown. Poor plumbing is often the cause of contaminated food. The gases which escape from unclean traps may carry with them solid particles of organic matter in various stages of decay. The "house side" of traps always ventilates into the rooms, and hence it is impor- tant that they be kept scrupulously clean. Where the drip pipe from the refrigerator drains directly into the sewerage system, there is always danger. Special atten- tion should be given to the care of plumbing near places where foods are stored. Frequently there are leaky joints due to settling of the dwellings or to extreme changes in temperature, and the plumbing should be occasionally inspected by one familiar with the sub- ject.ioo 290. General Considerations. — In order to keep food in the most wholesome condition, special care should be taken that all of its surroundings are sanitary. The air, the dishes in which the'f ood is placed, the refrigerator, cellar or closet where stored, and the other food with which it comes in contact, all influence the wholesome- ness or cause contamination. A food may contain sufficient nutrients to give it high value, and yet, on account of products formed during fermentation, be poisonous. Foods are particularly susceptible to putre- faction changes, and chemicals and preservatives added as preventives, with a view of retarding these changes. 298 HUMAN FOODS AND THEIR NUTRITIVE VALUE are objectionable, besides failing to prevent all fermenta- tion from taking place. Intelligent thought should be Fig. 71. — a Petri Dish, showing Colonies of Bacteria produced by allowing a house fly to crawl over surface. (From Minnesota Experiment Station Bulletin No. 93.) exercised in the care of food, for the health of the con- sumer is largely dependent upon the purity and whole- someness of the food supply. CHAPTER XXI LABORATORY PRACTICE Object of Laboratory Practice, Laboratory Note-book, and Sugges- tions for ^Laboratory Practice. — The aim of the laboratory practice is to give the students an idea of the composition, uses, and values of food materials, and the part vfhich chemistry takes in sanitation and household affairs ; also to enable them by simple tests to detect some of the more common adulterants in foods. Before performing an experiment, the student is advised to review those topics presented in the text which have a bearing upon the experiment, so that a clear conception may be gained of the relation- ship between the laboratory work and that of the class room. The student should endeavor to cultivate the power of observation and to grasp the principle involved in the work, rather than do it in a merely mechanical and perfunctory way. Neatness is one of the essentials for success in laboratory practice, and too much emphasis cannot be laid upon this requisite to good work. The student should learn to use his time in the laboratory profitably and economically. He should obtain a clear idea of what he is to do, and then do it to the best of his ability. If the experiment is not a success, repeat it. While the work is in progress it should be given undivided attention. Care should be exercised to prevent anything getting into the sinks that will clog the plumbing ; soil, matches, broken glass, and paper should be deposited in the waste jars. A careful record of the experiments should be kept by each student in a suitable note-book. It is suggested that those students desiring more time in writing out the experiments than the laboratory period affords, take notes as they make the various tests, and then amplify and rearrange them in the evening study time. The final writing up of the notes should, however, be done before the next laboratory 299 300 HUMAN FOODS AND THEIR NUTRITIVE VALUE period. Careful attention should be given to the spelling, language, and punctuation, and the note-book should represent the student's individual work. He who attempts to cheat by copying the results Fig. 72. — Apparatus used in Laboratory Work. See page 301 for names. of others, only cheats himself. In recording the results of an experi- ment, the student should state briefly and clearly the following: 1. Number and title of experiment. 2. How the experiment is performed. 3. What was observed. ■ 4. What the experiment proves. LABORATORY PRACTICE 301 Fig. 73. — Balance and Weights. List of Apparatus used 1 Crucible Tongs 2 Evaporating Dishes I Casserole ■6 Beakers 12 Test Tubes I Wooden Stand I Test Tube Stand 1 Sand Bath 2 Funnels I Tripod I Stoddart Test Tube Clamp IN EXPERIJIENTS I Test Tube Brush 1 Burner and Tubing 2 Stirring Rods 6 Watch Glasses 2 Erlenmeyer Flasks I Package Filter Paper I Box Matches 1 Wire Gauze 2 Burettes I Porcelain Crucible I Aluminum Dish 302 HUMAN FOODS AND THEIR NUTRITIVE VALUE ^^^ B'lG. 74. Directions for Weighing. — Place the dish or material to be weighed in the left-hand pan of the balance. With the forceps lay a weight from the weight box on the right-hand pan. Do not touch the weights with the hands. If the weight selected is too heavy, replace it with a lighter weight. Add weights until the pans are counter- poised ; this will be indicated by the needle swinging nearly as many divisions on one side of the scale as on the other. The brass weights are the gram weights. The other weights are fractions of a gm. The 50G, 200, 100 mg. (milligram) weights are recorded as 0.5, 0.2, and U.I gm. The 50, 20, and 10 mg. weights as 0.05, 0.02, and o.oi gm. If the 10, and 2 gm., and the 200, the 100, and the 50 mg. weights are used, the resulting weight is 12.35 S™^- ^° moist substances should ever come in contact with the scale pans. The weights and forceps should always be replaced in the weight box. Too much care and neatness cannot be exercised in weighing. Directions for Measuring. — Reagents are measured in gradu- ated cylinders (see Fig. 74). When the directions call for the addition of 5 or 10 cc. of a re- agent, unless so directed it is not absolutely necessary to measure the reagent in a measuring cyl- inder. A large test tube holds about 30 cc. of water. Measure out 5 cc. of water and transfer jt to a large test tube. Note Fig. 75 its volume. Add approximately 5 cc. of water directly to the test tube. Measure it. Repeat this operation until you can judge with a fair degree of accuracy the part of a test tube filled b>' 5 cc. In the experiments where a -Pouring Reagent from Bottle. LABORATORY PRACTICE 303 burette is used for measuring reagents, the burette is first filled with the reagent by means of a funnel. The tip of the burette is allowed to fill before the readings are made, which are from the lowest point or meniscus. When reagents are removed from bottles, the stopper Fig. 76. — Microscope and Accessories. I, eye-piece or ocular ; 2, objective; 3, stage; 4, cover glass ; 5, slide; 6, mirror. should be held between the first and second fingers of the right hand (see Fig. 75). Hold the test tube or receptacle that is to receive the reagent in the left hand. Pour the liquid slowly until the desired amount is secured. Before inserting the stopper, touch it to the neck of the bottle to catch the few drops on the edge, thus pre- venting their streaking down the sides of the bottle on to the shelf. 304 HUMAN FOODS AND THEIR NUTRITIVE VALUE Replace the bottle in its proper place. Every precaution should be taken to prevent contamination of reagents. Use of the Microscope. — Special directions in the use of the micro- scope will be given by the instructor. The object or material to be examined is placed on a microscopical slide. Care should be exer- cised to secure a representative sample, and to properly distribute the substance on the slide. If a pulverized material is to be exam- ined, use but little and spread it in as thin a layer as possible. If a liquid, one or two drops placed on the slide will suffice. The mate- rial on the slide is covered with a cover glass, before it is placed on the stage of ilie microscope. In focusing, do not allow the object glass 01 'i uiicroscope to come in contact with the cover glass. Focus upward, not downward. Special care should be exercised in focusing arid in handling the eye-piece and objective. A camel's-hair brush, clean dry chamois skin, or clean silk only should be used in polishing the lenses. Always put the microscope back in its case after using: Experiment No. i Water in Flour Carefully weigh a porcelain or aluminum dish. (Porcelain must be used if the ash is to be determined on the same sample.) Place in it about 2 gm. of flour; record the weight; then place the dish in the water oven for at least 6 hours. After drying, weigh again, and from the loss of weight calculate the per cent of water in the flour. (Weight of flour and dish before drying minus weight of flour and dish after drying equals weight of water lost. Weight of water divided by weight of flour taken, muldplied by ifco, equals the per cent of water in the flour.) How does the amount of water you obtained compare with the amount given in the tables of analysis ? LABORATORY PRACTICE 305 Experiment No. 2 )( Water in Butter CareftiUy weigh a clean, dry aluminum dish, place in it about 2 gms. of butter, and weigh again. Record the weights. Place the dish containing butter in the water oven for 5 or 6 hours and then weigh. The loss in weight represents the water in the butter. Calculate the per cent of water. Care must be taken to get a representative sample of the butter to be tested ; preferably small amounts should be taken with the butter trier from various parts of the package. Experiment No. 3 Ash in Flour Place the porcelain dish containing flour from the preceding ex- periment in a muffle furnace and let it remain until the organic matter is completely volatilized. Cool, weigh, and determine the per cent of ash. The flour should be burned at the lowest temperature necessary for complete combustion. Experiment No. 4 ^ Nitric Acid Test for Nitrogenous Organic Matter To 3 cc. of egg albumin in a test tube add 2 cc. of HNO3 (cone.) and heat. When cool add NH^OH. The nitric acid chemically reacts upon the albumin, forming yellow xanthoprotein. What change occurs in the appearance of the egg albumin when the HNO3 is added? Is this a physical or chemical change? What is the name of the compound formed? What change occurs on adding NH^H? \( Experiment No. 5 Acidity of Lemons With a pipette measure into a small beaker 2 cc. of lemon juice. Add 25 cc. of water and a few drops of phenolphthalein indicator. X 3o6 HUMAN FOODS AND THEIR NUTRITIVE VALUE From the burette run in N/io KOH solution until a faint pink tinge remains permanently. Note the number of cubic centimeters of KOH solution required to neutralize the citric acid in the lemon juice. Calculate the per cent of citric acid. (i cc. of N/io KOH solution equals 0.00642 gm. citric acid. I cc. of H.fl weighs i gm. Because of sugar and other matter in solution I cc. of lemon juice weighs approximately 1.03 gm.) I. What is the characteristic acid of lemons? 2. What is the salt formed when the lemon juice is neutralized by the KOH solu- tion? 3. Describe briefly the process for determining the acidity of lemon juice. 4. What per cent of acidity did you obtain ? 5. How does this compare with the acidity of vinegar? / Experiment No. 6 Influence of Heat on Potato Starch Grains With the point of a knife scrape slightly the surface of a raw potato and place a drop of the starchy juice upon the microscopi- cal slide. Cover with cover glass and examine under the micro- scope. In the evaporating dish cook a small piece of potato, then place a very small portion upon the slide, and examine with the microscope. JVIake drawings of the starch grains in raw and in cooked potatoes. / Experiment No. 7 Influence of Yeast on Starch Grains Moisten a small portion of the dough prepared with yeast and with the stirring rod place a drop of the starchy water upon the slide. Cover with cover glass and examine under the micro- scope. Repeat, examining a drop of starchy water washed from flour. Make drawing of wheat starch grain in flour and in dough pre- pared with yeast. LABORATORY PRACTICE 307 Experiment No. 8 Mechanical Composition of Potatoes Wash one potato. Weigh, then peel, making the peeling as thin as possible. Weigh the peeled potato and weigh the peeling or refuse. Calculate the per cent of potato that is edible and the per cent that is refuse. . Experiment No. 9 Pectose from Apples Reduce a small peeled apple to a pulp. Squeeze the pulp through a clean cloth into a beaker. Add 10 cc. H^O and heat on a sand bath to coagulate the albumin. Filter, adding a little hot water if necessary. To the filtrate add 5 cc. alcohol. The precipitate is the pectose material. I. Is the pectose from the apple soluble? 2. Is it coagulated by heat? 3. Is it soluble in alcohol? Experiment No. 10 Lemon Extract To 5 cc. of the extract in a test tube add an equal volume of water. A cloudy appearance indicates the presence of lemon oil. If the solution remains clear after adding the water, the extract does not contain lemon oil. Why does the extract containing lemon oil become cloudy on adding water? f. Experiment No. 11 Vanilla Extract Pour into a test tube 5 cc. of the extract to be tested. Evaporate to one third. Then add sufficient water to restore the original vol- ume. If a brown, flocculent precipitate is formed, the sample con- tains pure vanilla extract. Resin is present in vanilla beans and is extracted in the essence. The resin is readily soluble in 50 per cent 3o8 HUMAN FOODS AND THEIR NUTRITIVE VALUE alcohol. If the alcohol is removed from the extract, the excess of resin is precipitated, or if free from alkali, it may be precipitated by diluting the original solution with twice its volume of water. Test the two samples and compare. (Adapted from Leach, " Food Inspection and Analysis.") 1 . Describe the appearance of each sample after evaporating and adding water. 2. Which sample contains pure vanilla extract? 3. State the principle underlying this test. Experiment No. 12 \ Testing Olive Oil for Cotton Seed Oil Pour into a test tube 5 cc. of the oil to be tested and 5 cc. of Halphen's Reagent. Mix thoroughly. Plug the test tube loosely with cotton, and heat in a bath of boiling saturated brine for 15 minutes. If cotton seed oil is present, a deep red or orange color is produced. Test two samples and compare. Halphen's Reagent. — Mix equal volumes of amyl alcohol and car- bon disulphid containing about one per cent of sulphur in solution. (.Adapted from Leach, " Food Inspection and .Analysis.") Experiment No. 13 "'^ Testing for Coal Tar Dyes Dilute 20 to 30 cc. of the material to 100 cc. ; boil for 10 minutes with 10 cc. of a 10 per cent solution of potassium bisulphate and a piece of white woolen cloth which has previously been boiled in a 0.1 per cent solution of NaOH and thoroughly washed in water. Remove the cloth from the solution, wash in boiling water, and dry between pieces of filter paper. A bright red indicates coal tar dye. If the coloring matter is entirely from fruit, the woolen cloth will be either uncolored or will have a faint pink or brown color which is changed to green or yellow by ammonia and is not restored by washing. This is the Arata test. (Adapted, Winston, Conn. Experiment Station Report.) LABORATORY PRACTICE 309 I. Describe Arata's wool test for coal tar dyes. 2. What is the appearance of the woolen cloth when the coloring matter is entirely from fruit ? 3. What effect has NH^H upon the color ? 4. Why is NaOH used ? 5. Why may not cotton cloth be used instead of woolen ? 6. What can you say of the use of coal tar dyes in foods ? Experiment No. 14 (( Determining the Per Cent of Skin in' Beans Place in an evaporating dish 10 gm. of beans, 50 cc. of water, and } gm. of baking soda. Boil 10 minutes or until the skins are loosened, then drain off the water. Add cold water and rub the beans together till the skins slip off. Collect the skins, place on a watch glass and dry in the water oven for ^ hour. Weigh the dried skins and calculate the per cent of "skin." I. What does the soda do? 2. What effect would hard lime- water have upon the .skins ? 3. How does removal of skins affect food value of beans and digestibility ? Experiment No. 15 X Extraction of Fat from Peanuts Shell three or four peanuts and with the mortar and pestle break them into small pieces. Place in a test tube and pour over them about 10 cc. of ether. Cork the test tube and allow it to stand 30 minutes, shaking occasionally. Filter on to a watch glass and let stand until the ether evaporates, and then observe the fat. I. What is the appearance of the peanut fat ? 2. What is the solvent of the fat ? 3. What becomes of the ether ? 4. Why should the peanuts be broken into small pieces ? Experiment No. 16 Microscopic Examination of Milk Place a drop of milk on a microscopical slide and cover with cover glass. Examine the milk to detect impurities, as dust, hair, refuse, etc. Make drawings of any foreign matter present. 3IO HUMAN FOODS AND THEIR NUTRITIVE VALUE Experiment No. 17 / Formaldehyde in Cream or Milk To 10 cc. of jnilk in a casserole add 10 cc. of the acid reagent. Heat slowly over the flame nearly to boiling, holding the casserole in the hand and giving it a slight rotary movement while heating. The presence of formaldehyde is indicated by a violet coloration varying in depth with the amount present. In the absence of formaldehyde the solution slowly turns brown. Acid Reagent. — Commercial hydrochloric acid (spgr. 1.2) con- taining 2 cc. per liter of lo per cent ferric chlorid. (Adapted from Leach, " Food Inspection and Analysis.") I. How may the presence of formaldehyde in milk be detected? 2. Why in this test is it necessary to use acid containing ferric chlorid ? 3. Describe the appearance of the two samples of milk after adding the acid reagent and heating. 4. Which sample showed the presence of formaldehyde ? Experiment No. 18 Gelatine in Cream or Milk To 20 cc. of milk or cream in a beaker add 20 cc. of acid mercuric nitrate and about 40 cc. of H2O. Let stand for a few minutes and filter. Filtrate will be cloudy if gelatine is present. Add J cc. of a dilute solution of picric acid — a heavy yellow precipitate indicates gelatine. Acid Mercuric Nitrate. — i part by weight of Hg, 2 parts HNO3 (sp. gr. 1.42). Dilute 25 times with water. 4- Experiment No. 19 Testing for Oleomargarine Apply the following tests to two samples of the material : Boiling or Spoon Test. — Melt the sample to be tested — a piece about the size of a chestnut — in a large spoon, hastening the LABORATORY PRACTICE 3II process by stirring with a splinter. Then, increasing the heat, bring to as brisk a boil as possible and stir thoroughly, not neglect- ing the outer edges. Oleomargarine and renovated butter boil noisily, sputtering like a mixture of grease and water, and produce no foam, or but very little. Genuine butter boils with less noise and produces an abundance of foam. Waterhouse Test. — Into a small beaker pour 50 cc. of sweet milk. Heat nearly to boiling and add from 5 to 10 gms. of butter or oleomargarine. Stir with a glass rod until fat is melted. Then place the beaker in cold water and stir the milk until the tempera- ture falls sufficiently for the fat to congeal. At this point the fat, if oleomargarine, can easily be collected into one lump by means of the rod ; while if butter, it will granulate and cannot be collected. (From Farmers' Bui. 131, U. S. Dept. of Agriculture.) I. Name two simple tests for distinguishing butter and oleomar- garine. 2. Describe these tests. 3. Why do butter and oleomar- garine respond differently to these tests ? 4. Are these tests based upon chemical or physical properties of the fats ? Experiment No. 20 Testing for Watering or Skimming of Milk a. Fat Content of Milk by Means of Babcock Test. — Measure with pipette into test bottle 17.6 cc. of milk. Sample should be carefully taken and well mixed. Measure with cylinder 17.5 cc. commercial HjSO^ and add to milk in test bottle. (See Fig. 25.) Mix acid and milk by rotating the bottle. Then place test bottles in centrifugal machine and whirl 5 minutes. Add sufficient hot water to test bottles to bring contents up to about the 8th mark on stem. Then whirl bottles 2 minutes longer and read fat. Read from extreme lowest to highest point. Each large division as i to 2 represents a whole per cent, each small division 0.2 of a per cent. b. Determining Specific Gravity by Means of Lactometer. — Pour 150 cc. of milk into 200 cc. cyhnder. Place lactometer in milk and 312 HUMAN FOODS AND THEIR NUTRITIVE VALUE note depth to which it sinlcs as indicated on stem. Note also tem- perature of millc. For each io° above 60° F. add i to the lactometer number, in order to make the necessary correction for temperature. For example, if milk has sp. gr. of i .032 at temperature of 70°, it will be equivalent to sp. gr. of 1.033 at 60°. Ordinarily milk has a sp. gr. of 1.029 to 1.034. If milk has sp. gr. of less than 1.029, or contains less than 3 per cent fat, it may be considered watered milk. If the milk has a high sp. gr. (above 1.035) ^^^ ^ 'o^ content of fat, some of the fat has been removed. (For extended direction for milk testing see Snyder's " Dairy Chemistry.") / Experiment No. 21 Boric Acid in Meat Cut into very small pieces 5 gms. of meat, removing all the fat possible. Place in an evaporating dish with 20 to 25 cc. of water to which a few drops of HCl have been added and warm slightly. Dip a piece of turmeric paper in the meat extract and dry. A rose- red color of the turmeric paper after drying (turned olive by a weak ammonia solution) is indicative of boric acid. I. How may meat be tested for boric acid? 2. Why is HCl added to the water? 3. Why is the water containing the meat warmed slightly? 4. What is the appearance of the turmeric paper after being dipped in the meat extract and dried? 5. What change takes place when it is moistened with ammonia, and why? Experiment No. 22 I Microscopic Examination of Cereal Starch Grains Make a microscopic examination and drawings of wheat, corn, rice, and oat starch grains, comparing them with the drawings of the different starch grains on the chart. If the material is coarse, pul- verize in a mortar and filter through cloth. Place a drop or two of the starchy water on the slide, cover with a cover glass, and ex- amine. LABORATORY PRACTICE 313 Experiment No. 23 Identification of Commercial Cereals Examine under the microscope two samples of cereal breakfast foods, and by comparison with the wheat, corn, and oat starch grains previously examined tell of what grains the breakfast foods are made and their approximate food value. Experiment No. 24 Granulation and Color of Flour Arrange on glass plate, in order of color, samples of all the differ- ent grades of flour. Note the differences in color. How do these differences correspond with the grades of the flour? Examine the flour with a microscope, noting any coarse or dark-colored particles of bran or dust. Rub some of the flour between the thumb and fore- finger. Note if any granular particles can be detected. Experiment No. 25 Capacity of Flour to absorb Water Weigh out 15 gms. of soft wheat flour into an evaporating dish ; then add from burette a measured quantity of water sufficient to make a stiff dough. Note the amount of water required for this purpose. Repeat the operation, using hard wheat flour. I. Howmay the absorptivepower of a flour be determined? 2. To what is it due? 3. Why do some flours absorb more water than others ? Experiment No. 26 Acidity of Flour Weigh into a flask 20 gms. of flour and add 200 cc. distilled water. Shake vigorously. After letting stand 30 minutes, filter and then titrate 50 cc. of the filtrate against standard KOH solution, using phenolphthalein as indicator, i cc. of the alkali equals 0.009 gms. lactic acid. Calculate the per cent of acid present. 314 HUMAN FOODS AND THEIR NUTRITIVE VALUE I. How may the acidity of a flour be determined? 2. The acid- ity is expressed in percentage amounts of what acid? 3. What per cent of acidity is found in normal flours? 4. What does a high acidity of a flour indicate ? Experiment No. 27 Moist and Dry Gluten Weigh 30 gm. of flour into a porcelain dish. Make the flour into a stiff" dough. After 30 minutes obtain the gluten by washing, being careful to remove all the starch and prevent any losses. Squeeze the water from the gluten as thoroughly as possible. Weigh the moist gluten and calculate the per cent. Dry the gluten in the water oven and calculate the per cent of dry gluten. Experiment No. 28 Gliadin from Flour Place in a flask 10 gms. of flour, 30 cc. of alcohol, and 20 cc. of water. Cork the flask and shake, and after a few minutes shake again. Allow the alcoliol to act on the flour for an hour, or until the next day. Then filter off the alcohol solution and evaporate the filtrate to dryness over the water bath. Examine the residue ; to a portion add a little water ; burn a small portion and observe odor. I. Describe the appearance of the gliadin. 2. What was the re- sult when water was added? 3. When burned, what was the odor of the gliadin, and what does this indicate? 4. What is gliadin? Experiment No. 29 Bread-making Test Make a " sponge " by mixing together : 12 gm. sugar, 12 gm. yeast (compressed), 4 gm. salt, 175 cc. water (temp. 32° C). LABORATORY PRACTICE 315 Let stand J hour at a temperature of 30° C. In a large bowl, mix with a knife or spatula 7.7 gms. of lard with 248.6 gms. of flour. Then add 160 cc. of the " sponge,'' or as much as is needed to make a good stiff dough, and mix thoroughly, using the spatula. With some flours as small a quantity as 150 cc. of sponge, may be used. If more moisture is necessary, add H.1O. Keep at temperature of 30" C. Allow the dough to stand 50 minutes to first pulling, 40 min- utes to second pulhng, and 30 to 50 minutes to the pan. Let it rise to top of pan and then bake for | hour in an oven at a temperature of 180° C. One loaf of bread is made of patent flour of known quality as a standard for comparison, and other loaves of the flours to be tested. Compare the loaves as to size (cubic contents), color, porosity, odor, taste, nature of crust, and form of loaf. Experiment No. 30 Microscopic Examination of Yeast On a watch glass mix thoroughly a very small piece of yeast with about 5 cc. of water and then with the stirring rod place a drop of this solution on the microscopical sUde, adding a drop of very dilute methyl violet solution. Cover with the cover glass and examine under the microscope. The living active cells appear color- less while the decayed and lifeless ones are stained. Yeast cells are circular or oval in shape. (See Fig. 46.) (Adapted from Leach, " Food Inspection and Analysis.") Experiment No. 31 Testing Baking Powders for Alum Place about 2 gms. of flour in a dish with | gm. baking powder. Add enough water to make a dough and then 2 or 3 drops of tincture of logwood and 2 or 3 drops of ammonium carbonate solution. iVIix well and observe ; a blue color indicates alum. Try the same test, using flour only for comparison. 3l6 HUMAN FOODS AND THEIR NUTRITIVE VALUE I. How do you test a baking powder for alum ? 2. What differ- ence in color did you observe in the test with the baking powder containing alum and in that with the flour only? 3. Why is the (NH4)2C03 solution used? Experiment No. 32 Testing Baking Powders for Phosphoric Acid Dissolve J gm. of baking powder in 5 cc. of H2O and 3 cc. HNO3. Filter and add 3 cc. ammonium molybdate. Heat gently. A yellow precipitate indicates phosphoric acid. I. How do you test a baking powder for phosphoric acid? 2. What is the yellow precipitate obtained in this test? Experiment No. 33 Testing Baking Powders for Ammonia Dissolve ^ gm. of material in 10 cc. water ; filter off any in- soluble residue and to the filtrate add 2 or 3 cc. NaOH and apply heat. Test the gas given off with moistened turmeric paper. If NH3 is present, the paper will be colored brown. Do not allow the paper to come in contact with the liquid or sides of the test tube. (Perform the tests on two samples of baking powder.) I. How do you test a baking powder for ammonia? .;. Why do you add NaOH? 3. Why must you be careful not to let the tur- meric paper touch the sides of the test tube or the liquid ? Experiment No. 34 ' Vinegar Solids Into a weighed aluminum or porcelain dish pour 10 cc. of vinegar. Weigh and then evaporate over boiling water. To drive off the last traces of moisture dry in the water oven for an hour. Cool and weigh. Calculate the per cent of solids. Observe the appearance of the solids. Test both samples and compare. LABORATORY PRACTICE 317 I. How may the per cent of solids in vinegar be determined? 2. Describe tlie appearance of the solids fi-om the good and from the poor sample of vinegar. 3. What is the legal standard for vinegar solids in your state? Experiment No. 35 Specific Gravity of Vinegar Pour 170 cc. vinegar into 200 cc. cylinder. Place a hydrometer for heavy liquids (sp. gr. 1 to i.i) in the cylinder. Note the depth to which it sinks and the point registered on the scale on the stem. Note temperature of vinegar. Record Specific gravity of vine- gar. I. What effect would addition of water to vinegar have upon its specific gravity? 2. What effect would addition of such material as sugar have upon specific gravity? 3. Why should the specific gravity of vinegar be fairly constant? 4. What would be the weight of 1000 cc. of vinegar calculated from the specific gravity? Experiment No. 36 Acidity of Viilegar Into a small beaker pour 6 cc. of vinegar and 10 cc. of water and a few drops of phenolphthalein indicator. Run m standard KOH solution from a burette until a faint pink tinge remains permanently. Note the number of cubic centimeters of KOH solution required to neutralize the acid. Divide this number, by 10, which will give approximately the per cent of acetic acid. I. How may the per cent of acidity of vinegar be determined? 2. Why was phenolphthalein used? 3. Why was KOH used? 4. What acids does vinegar contain? 5. What is the legal re- quirement in this state for acetic acid in vinegar? 6. How did the acidity you obtained compare with this legal require- ment? 3l8 HUMAN FOODS AND THEIR NUTRITIVE VALUE Experiment No. 37 Deportment of Vinegar with Reagents To 10 cc. of vinegar in a test tube add 8 or 10 drops of lead sub-acetate and shake. Observe the precipitate. Lead sub-acetate precipitates mainly the malic acid which is always present in cider vinegar. I. How may the presence of malic acid in a vinegar be detected? 2. Describe the precipitate. 3. What does malic acid in a vinegar indicate? Experiment No. 38 Testing Mustard for Turmeric Place I gm. of ground mustard on a small watch glass and moisten slightly with water. Add 2 or 3 drojDs of NH^OH, stirring well with a glass rod. A brown color indicates turmeric present in con- siderable quantit)'. Test a sample of good mustard and one adulterated with turmeric and compare the results. Experiment No. 39 Examination of Tea Leaves Soak a small amount of tea and unroll 8 or 10 of the leaves. Make a drawing of a tea leaf. Observe the proportion of stems in each of three samples of tea ; also the relative proportion of large and small leaves. Observe if the leaves are even as to size and of a uniform color. Experiment No. 40 ' Action of Iron Compounds upon Tannic Acid Make an infusion of tea by placing 3 gms. of tea in 100 cc. of hot water and stirring well. Filter off some of the infusion and test 5 cc. with ferrous sulphate solution made by dissolving i gm. FeSO^ in 10 cc. HoO and filtering. Note the result. LABORATORY PRACTICE 3I9 I . What change in color did you observe when the ferrous sul- phate solution was added to the tea infusion ? 2. What effect would waters containing iron have upon the tea infusion ? Experiment No. 41 Identification of Coffee Berries Examine Rio, Java, and Mocha coffee berries. Describe each. Note the characteristics of each kind of coffee berry. Experiment No. 42 Detecting Chicory in Coffee Fill a beaker with water and place about a teaspoonful of ground coffee on the surface. If much of the ground material sinks and it imparts a dark brown color to the lower portion of the liquid, it is an indication of the presence of chicory. Pure coffee floats on water. Chicory has a higher specific gravity than coffee. I. How may the presence of chicory in ground coffee be de- tected? 2. Why does coffee float on the water while chicory sinks? 3. What effect does chicory have upon the color of water? Experiment No. 43 Testing Hard and Soft Waters Partially fill a large cylinder with very hard water. This may be prepared by dissolving o.i to 0.2 gm. calcium chloride in 500 cc. of ordinary water. Add to this a measured quantity of soap solu- tion. Mix well and notice how many cubic centimeters of soap so- lution must be used before a permanent lather is formed, also notice the precipitate of "lime soap.'' Repeat this experiment, using either rain or distilled water, and compare the cubic centimeters of soap solution used with that in former test. Repeat the test, using tap water. Soap Solution. — Scrape 10 gms. of castile soap into fine shavings 320 HUMAN FOODS AND THEIR NUTRITIVE VALUE and dissolve in a liter of alcohol, dilute with | water. Filter if not clear and keep in a tightly stojjpered bottle. I. Why is more soap required to form a lather with hard water than with soft water? i. What is meant by "lime soap"? De- scribe its appearance. 3. How may hard waters be softened for household purposes? Experiment No. 44 Solvent Action of Water on Lead Put I gm. of clean bright lead shavings into a test tube contain- ing 10 cc. of distilled water. After 24 hours decant the clear liquid into a second test tube, acidify slightly with HCL, and add a little hydrogen sulphid water. A black or brownish coloration indicates lead in solution. (Adapted from Caldwell and Breneman, "Introductory Chemical Practice.") Under what conditions may lead pipes be objectionable? Experiment No. 45 Suspended Matter in Water Place a drop of water on the microscopical slide, cover with cover glass, and e.^amine with the microscope. Note the occurrence and appearance of any suspended matter in the water. Experiment No. 46 Organic Matter in Water Pour into the e^'aporating dish 100 cc. H.,0 and evaporate to dryness over the sand bath. Ignite the solids. If the solids blacken when ignited, the water contains organic matter. Experiment No. 47 Deposition of Lime by Boiling Water Boil for a few minutes about 200 cc. of water in a flask. After the water is cool, note any sediment of lime or turbidity of the water due to expelling the carbon dioxid. LABORATORY PRACTICE 32 1 I. What is meant by a "hard" water? 2. What do the terms '• temporary " and " permanent " hardness of water mean ? 3. What acts as ci solvent of the lime in water? 4. Why does boiling cause the lime to be deposited ? Experiment No. 48 Qualitative Tests for Minerals in Water Test for Chlorids. — To 10 cc. of Hfi add a few drops of HNO, and 2 cc. of AgNO^. A white precipitate indicates the presence of chlorids, usually in the form of sodium chlorid. Test for Sulphates. — To 10 cc. of water add 2 cc. of dilute HCl and 2 cc. of BaCU. A cloudiness or the formation of a white pre- cipitate indicates the presence of sulphates. Test for Iron. — If a brow n sediment is formed in water exposed to the air for some time, it is probably iron hydroxid. To 10 cc. of the water add a few drops of HNO;., heat, and then add ^ cc. of NH4CNS. A red color indicates the presence of iron. Test for CaO and MgO. — To 10 cc. of H^O add 5 cc. NH^OH. If a precipitate forms, filter it off, and to the filtrate add 3 cc. NH^Cl and 5 cc. (NH4)2C204. The precipitate is CaCjO^, and the filtrate contains the magnesia. Filter and add 5 cc. Na,,P04 to precipitate MgNH.PO^. I. How would you test a water to detect the presence of organic matter? 2. Name some mineral impurities often found in water. 3. Describe the test for chlorids ; for sulphates ; for iron ; for lime ; for magnesium. 4. Of the two classes of impurities found in water, which is the more harmful? 5. Name three ways of purifying waters known to be impure, and tell which is the most effectual. Experiment No. 49 Testing for Nitrites in Water To 50 cc. of water in a small beaker add with a pipette 2 cc. of naphthylamine hydrochloride and then 2 cc. of sulphanilic acid. Y 32 2 HUMAN FOODS AND THEIR NUTRITIVE VALUE Stir well and wait 20 minutes for color to develop. A pink color in- dicates nitrites. Reagents Used Sulphanilic Acid. — Dissolve 5 gm. in 150 cc. of dilute acetic acid; sp. gr. 1.04. Naphthylamine Hydrochloride. — Boil o.i gm. of solid a-amido- naphthaline (naphthylamine) in 20 cc. of water, filter the solution through a plug of absorbent cotton, and mix the filtrate with 180 cc. of dilute acetic acid. All water used must be free from nitrites, and all vessels must be rinsed out with such water before tests are applied. I. Would a water showing the presence of nitrites be a safe drink- ing water? Why? 2. What are nitrites? 3. What does the pres- ence of nitrites indicate? 4. Are small amounts of nitrites, when not associated with bacteria, injurious ? REVIEW QUESTIONS CHAPTER I General Composition of Foods I. To what extent is water present in foods? 2. Wliat foods contain the most, and what foods the least water? 3. How does the water content of some foods vary with the hydroscopicity of the air? 4. How may changes in water content of foods affect their weight? 5. Why is it necessary to consider the water content of foods in assigning nutritive values? 6. How is the dry matter of a food de- termined? 7. Why is the determination of the water in a food often a difficult process? 8. What is the ash or mineral matter of a food? 9. How is it obtained? 10. What is its source? 11. Of what is the ash of plants composed? 12. What part in plant life do these ash elements take? 13. Name the ash elements essential for plant growth. 14. Which of the mineral elements take the most essential part in animal nutrition? 15. In what form are these elements usually considered most valuable? 16. Why is sodium chloride or common salt necessary for animal life? 17. How do food materials differ in ash content? 18. Define organic matter of foods. 19. How is it obtained? 20. Of what is it composed ? 21. Into what is the organic matter converted when it is burned? 22. Give the two large classes of organic compounds found in food materials. 23. Name the various subdivisions of the non-nitrogenous com- pounds. 24. What are the carbohydrates? 25. Give their general composition. 26. What is cellulose? 27. Where is it found? 28. What is its function in plants? 29. What is its food value? 30. In what way may cellulose be of value in a ration? 31. In what way may it impart a negative value to a ration ? 32. What is starch? 323 324 HUMAN FOODS AND THEIR NUTRITIVE VALUE 33. Where is it mainly found in plants? 34. Give the raeclianical structure of the starch grain. 35. Why is starch insoluble in cold water? 36. How do starch grains from different sources differ in structure? 37. What effect does heat have upon starch? 38. Define hydration of starch. 39. Under what conditions does this change take place? 40. What value as a nutrient does starch possess? 41. What is sugar? 42. How does it resemble and how differ in composition from starch ? 43. What are the pectose substances? 44. How are they affected by heat? 45. What food value do they possess? 46. What is nitrogen-free-extract? 47. How is it obtained? 48. How may the nitrogen-free-extract of one food differ from that of another? 49. What are the fats? 50. How do they differ in composition from the starches? 51. Why does fat when burned or digested produce more heat than starch or sugar? 52. Name the separate fats of which animal and vege- table foods are composed. 53. Give some of the physical character- istics of fat. 54. What is the iodine absorption number of a fat? 55. How does the specific gravity of fat compare with that of water? 56. Into what two constituents may all fats be separated? 57. What is ether extract? 58. How does the ether extract in fats vary in composition and nutritive value? 59. What are the organic acids? 60. Name those most commonly met with in foods. 61. What nutritive value do they possess? 62. What dietetic value? 63. What value are they to the growing plant? 64. What organic acids are found in animal foods? 65. What are the essential oils? 66. How do they differ from the fixed oils, or fats? 67. What prop- erty do the essential oils impart to foods ? 68. What food value do they possess? 69. What dietetic value ? 70. What are the mi.xed compounds? 71. How may a compound impart a negative value to a food? 72. What is the nutritive value of the non-nitrogenous compounds, taken as a class? 73. Why is it necessary that nitrogenous and non-nitrogenous compounds be blended in a ration? 74. What are the nitrogenous compounds? 75. How do they differ from the non-nitrogenous compounds? 76. Name the four subdivisions of the nitrogenous compounds. 77. What is REVIEW QUESTIONS 325 protein? 78. What is characteristic as to its nitrogen content? 79. What are some of the derivative products that can be obtained from the protein molecule ? 80. How does the protein content of animal bodies compare with that of plants? 81. Name the various subdivisions of the proteins. 82. What is albumin, and how may it be obtained from a food? 83. What is globulin, and how is it obtained from a food? 84. Give some examples of globulins. 85. What are the albuminates, and how are they affected by the action of acids and alkalies? 86. What are the peptones, and how do they differ from the albumins? 87. How are the peptones produced from other proteids ? 88. What are the insoluble proteids ? 89. Give an example. 90. Which of the proteids are found to the greatest extent in foods? 91. Why may proteids from different sources vary in their nutritive value? 92. What general change do the proteids undergo during digestion? 93. What is crude protein? 94. How is the crude protein content of a food calculated? 95. Why is the nitrogen content of a food more absolute than the crude protein content? 96. What food value do the proteins possess? 97. Why may proteins serve so many functions in the body? 98. Why is protein necessary as a nutrient ? 99. What is the effect of an excess of protein in the ration ? 100. What is the effect of a scant amount of protein in a ration? loi. What are the albuminoids? 102. Name some materials that contain large amounts of albuminoids. 103. What food value do the albuminoids possess ? 104. What are the amids? 105. How are they formed in plants? 106. What is their source in animals? 107. What general changes does the element nitrogen undergo in plant and animal bodies ? 108. What is the food value of the amids? 109. What are the alkaloids ? no. What is their food value? in. What effect do some alkaloids exert upon the animal body? 112. How may they be produced in animal foods? 113. What general relationship exists between the various nitrogenous compounds? 114. Why is it essential that the animal body be supplied with nitrogenous food in the form of pro- teids? 115. Name the cycle of changes through which the element nitrogen passes in plant and animal bodies. 326 HUMAN FOODS AND THEIR NUTRITIVE VALUE CHAPTER 11 Changes in Composition of Foods during Cooking and Preparation 116. How do raw and cooked foods compare in general compo- sition? 117. In what ways are foods acted upon during coolcing? 118. Wiiat causes cliemical changes to take place during cook- ing? iig. What are the principal compounds that are changed during the process of cooking? 120. How does cooking affect the cellulose of foods? 121. What change does starch undergo during cooking? 123. When foods containing starch are baked, what change occurs? 123. How are the sugars acted upon when foods are cooked? 124. What effect does dry heat have upon sugar? 125. What change occurs to the fats during cooking? 126. How does this affect nutritive value? 127. What changes do the pro- teids undergo during cooking? 128. Why does the action of heat affect various proteids in different ways? 129. Why are chemical changes, as hydration, often desirable in the cooking and prepara- tion of foods? 130. What physical changes do vegetable and ani- mal tissues undergo when cooked? 131. How do foods change in weight during cooking? 132. Why is a prolonged high temperature unnecessary to secure the best results in cooking? 133. To what extent is the energy of fuels utilized for producing mechanical and chemical changes in foods during cooking? 134. What effect does cooking have upon the bacterial flora of foods? 135. In what ways do bacteria exert a favorable influence in the preparation of foods? 136. How may certain classes of bacteria exert unfavorable changes in the preparation of foods? 137. What are the insoluble fer- ments? 138. What are the soluble ferments? 139. What part do they take in animal and plant nutrition? 140. Define aerobic fer- ments. 141. Define anaerobic ferments. 142. What general rela- tionship exists between the chemical, physical, and bacteriological changes that take place in foods? 143. Why should foods also possess an esthetic value? 144. What kinds of colors should be REVIEW QUESTIONS 327 used in the preparation of foods ? 145. What processes should be used for removal of coloring materials from foods? CHAPTER III Vegetable Foods 146. Give the general composition of vegetable foods as a class. 147. How do vegetable foods differ from animal foods ? 148. Name some vegetables which contain the maximum, and some which contain the minimum percentage of protein. 149. Give the general composition of potatoes. 150. Of what is the dry matter mainly composed? 151. How much of the crude protein of potatoes is true protein ? 152. What ratio exists between the nitrogenous and non-nitrogenous compounds in the potato ? 153. Give the chemical composition of the potato. 154. What influence do different methods of boiling have upon the crude protein content of potatoes ? 155. To what extent are the nutrients of potatoes digested and absorbed by the body ? 156. What value do potatoes impart to the ration ? 157. How do sweet potatoes differ in chemical compo- sition and food value from white potatoes? 158. How do carrots differ in composition from potatoes ? 159. What is characteristic of the dry matter of the carrot ? 160. How do carrots and milk differ in composition ? 161. To what is the color of the carrot due ? 162. To what extent are the nutrients removed in the cooking of carrots? 163. What is the value of carrots in a ration ? 164. Give the characteristics of the composition of parsnips. 165. How does the starch of parsnips differ from that of potatoes? 166. How does the mineral matter of parsnips differ from that of potatoes ? 167. How does the cabbage differ in general composition from many vegetables ? 168. To what extent are nutrients extracted in the boiUng of cabbage ? 169. Give the nutritive value of cabbage. 170. How does the cauliflower differ from cabbage ? 171. Give the general composition of beets. 172. Give the general composition of cucumbers. 173. What nutritive value has lettuce ? 328 HUMAN FOODS AND THEIR NUTRITIVE VALUE 174. Give the composition and dietetic value of onions. 175. How does the ratio of nitrogenous and non-nitrogenous compounds in spinach differ from that in many other vegetables ? 176. Give the general composition and nutritive value of asparagus. 177. How much nutritive material do melons contain ? 178. What are the principal compounds of tomatoes ? 179. What nutrients do they supply to the ration? 180. In the canning of tomatoes, why is it desirable to conserve the juices ? 181. How does sweet corn dif- fer in composition from fully matured corn ? 182. What nutritive value does the egg plant possess ? 183. What are the principal nutrients of squash .^ 184. 'What nutritive material does celery contain? 185. To what does celery owe its dietetic value? 186. Why are vegetables necessary in a ration ? 187. Why is it not possible to value many vegetable foods simply on the basis of per- centage of nutrients present? 188. Name the miscellaneous com- pounds which many vegetables contain, and the characteristics which these may impart. 189. Why is it necessary to consider the sanitary conditions of vegetables ? 190. How do canned vegeta- bles differ in composition and food value from fresh vegetables ? 191. What proportion of vegetables is refuse and non-edible parts ? 192. Why is it necessary to consider the refuse of a food in determining its nutritive value ? CHAPTER IV Fruits 193. To what extent do fruits contain water and dry matter? 194. Give the general composition of fruits. 195. What compounds impart taste and flavor? 196. How much nutrients do fruits add to a ration? 197. Why is it not right to determine the value of fruits entirelyon the basis of nutrients? 198. Give the general composition of apples? 199. What compound is present to the greatest extent in the dry matter of apples? 200. How do apples differ in com- position? 201. Give the general physical composition of oranges. REVIEW QUESTIONS 329 202. What nutrients are present to the greatest extent in oranges? 203. How do lemons differ in composition from oranges? 204. How does grape fruit resemble and how differ in chemical composition from oranges and lemons? 205. What are the main compounds in strawberries? 206. In what ways are strawberries valuable in a ration? 207. Of what is grape juice mainly composed ? 208. What acid is in grapes, and what is its commercial value? 209. To what are the differences in flavor and taste due? 210. How do ripe olives differ in composition from green olives? 211. What is the food value of the olive? 212. What physiological property does olive oil have? 213. What is the principal nutrient in peaches ? 214. What compounds give flavor to peaches? 215. Of what does the dry matter of plums mainly consist? 216. How do plums differ in com- position from many other fruits? 217. What are prunes? What is their food value? 218. How do dried fruits differ in composition from fresh fruits? 219. What should be the stage of ripeness of fruit in order to secure the best results in canning? 220. How do canned fruits differ in composition and nutritive value from fresh fruits? 221. To what extent are metals dissolved by fruit juices? 222. Why should tin in which canned goods are preserved be of good quality? 223. What preservatives are sometimes used in the preparation of canned fruits ? 224. What is the objection to their use? 225. Why are fruits necessary in the ration? 226. What change does heat bring about in the pectose substances of fruits ? chapter v Sugar, Molasses, Sirups, Honey, and Confections 227. What is sugar? 228. From what sources are sugars ob- tained? 229. Name the two divisions into which sugars are divided. 230. How are sugars graded commercially? 231. What percent of purity has granulated sugar? 232. How is the coloring material of sugar removed? 233. How is sugar treated to make it whiter? 234. What value as a nutrient does sugar possess? 235. Why 330 HUMAN FOODS AND THEIR NUTRITIVE VALUE should sugar be combined with other nutrients ? 236. What foods contain appreciable amounts of sugar? 237. Why is an excessive amount of sugar in a ration undesirable? 238. Does sugar possess more than condimental value? 239. What is the average quantity of sugar consumed in this country? 240. What is maple sugar? 241. How does it differ in composition from other sugar? 242. How is adulterated maple sugar detected? 243. To what extent is gran- ulated sugar adulterated? 244. Why is it not easily adulterated? 245. What are the dextrose sugars? 246. How do they differ chemically from sucrose? 247. What is the inversion of sugar? 248. In what way does acid act upon sugar? 249. How are the acid products removed? 250. What is the food value of glucose? 251. What is molasses? 252. How is it obtained? 253. Of what is it composed? 254. What gives taste and flavor to molasses? 255. How may molasses act upon metalware? 256. What is the food value of molasses? 257. What is sirup? 258. Name three kinds of sirup, and mention materials from which they are pre- pared. 259. What is the polariscope, and how is it employed in sugar work? 260. What is honey? 261. How does it differ in composition from sugar? 262. How is strained honey adulterated? 263. What materials are used in the preparation of confections? 264. What changes take place in tlieir manufacture? 265. What materials are used for imparting color? 266. What can you say in regard to the coal tar colors? 267. What should be the position of candy in the dietary? 268. What can you say of the comparative value of cane and beet sugar? 269. How do the commercial grades of sugar compare as to nutritive value? 270. What are some of the impurities in candy? 271. What is saccharine? 272. What are its properties? CHAPTER VI Legumes and Nuts 273. What nutrients do the legumes contain in comparatively large amounts? 274. How does the amount of this nutrient com- REVIEW QUESTIONS 33I pare with that found in meats? 275. Why are legumes valuable crops in general farming and for the feeding of farm animals? 276. Give the general composition of beans. 277. How do beans compare in protein content with cereals? 278. How does the protein ofbeans differ from that of many other food materials? 279. To what extent are the nutrients of beans digested? 280. What influence does the combination of beans with other foods have upon digesti- bility? 281. What influence does removal of skins have upon digestibility? 282. In what part of the digestive tract are beans mainly digested? 283. How does the cost of the nutrients in beans compare with that of the nutrients in other foods? 284. How do string beans differ from green beans? 285. Give the general com- position, digestibility, and nutritive value of peas. 286. What can you say of the use of copper sulphate in the preparation of canned peas? 287. What nutrients do peanuts contain in large amounts? 288. Give the general composition of nuts. 289. What are the characteristics of pistachio? 290. Give the general com- position of the cocoanut. 291. What is cocoanut butter? 292. To what extent may nuts contribute to the nutritive value of a ra- tion? CHAPTER Vn Milk and Dairy Products 293. What can you say as to the importance of dairy products in the dietary? 294. Give the general composition of milk. 295. What compound in milk is most variable? 296. To what extent are the nutrients in milk digestible? 297. What influence does milk have upon the digestibility of other foods? 298. Why is cheese cured in cold storage? 299. How can the tendency of a milk diet to produce costiveness be overcome? 300. Why is it necessary to consider the .sanitary condition of milk? 301. What factors in- fluence the sanitary condition of milk? 302. What is certified milk? 303. What is pasteurized milk? 304. How can milk be pasteurized 33? HUMAN FOODS AND THEIR NUTRITIVE VALUE for family use ? 305 . What is tyrotoxicon ? 306. What is its source in millc? 307. To what is the color of milk due? 308. To what extent is color associated with fat content ? 309. What causes souring of milk? 310. What change occurs in the milk sugar? 311. What are the most favorable conditions for the sour- ing of milk ? 312. What are some of the preservatives used in milk. 313. What objection is urged against their use? 314. What is con- densed milk? 315. What is buttermilk, and what dietetic value has it? 316. How does goats' milk differ from cows' milk ? 317. What is koumiss, and how is it prepared? 318. What are the pre- pared milks? 319. How does human milk differ in composition from cows' milk? 320. Give the nutritive value of skim milk. 321. What content of fat should cream contain? 322. In what ways is milk adulterated ? 323. How are these adulterations de- tected ? 324. Give the general composition of butter. 325. What is the maximum amount of water that a butter may contain without being considered adulterated ? 326. What can you say in regard to the digestibility of butter ? 327. How is butter adulterated ? 328. How does oleomargarine compare in digestibility and food value with butter ? 329. What is the food value of butter ? 330. How does cheese differ in composition from butter? 331. Give the general composition of cheese. 332. To what are the flavor and odor of cheese due ? 333. Why is cheese ripened ? 334. What chemical changes take place during ripening ? 335. To what extent are the nutrients of cheese digested ? 336. Why is cheese some- times considered indigestible? 337. To what extent do the nu- trients of different kinds of cheese vary in digestibility ? 338. How does cheese compare in nutritive value and cost with meats ? 339. What is cottage cheese ? 340. What is Roquefort cheese ? 341 . Name four kinds of cheese, and say to what each owes its individuality. 342. How is cheese adulterated? 343. Why are dairy products in older agricultural regions generally cheaper than meats ? REVIEW QUESTIONS 333 CHAPTER Vin Meats and Animal Food Products 344. Give the general composition of meats. 345. How do meats diflfer in chemical composition from vegetable foods ? 346. What is the principal non-nitrogenous compound of meats, and what of vegetables ? 347. Name the different classes of proteins in meats. 348. Which class is present in largest amounts ? 349. To what extent are amid compounds present in meats ? 350. What characteristics do amids impart to meats ? 351. How are alkaloids produced in meats ? 352. In what ways does the lean meat of different kinds of animals vary chemically and physically ? 353. Give the general composition of beef. 354. What relationship ex- ists between the fat and water content of beef? 355. How much refuse have meats ? 356. In what forms are the ash elements (mineral matter) present in meats ? 357. How does veal differ in composition from beef ? 358. What general changes in composi- tion occur as animals mature ? 359. How do these compare with the changes that take place when plants ripen and seeds are pro- duced ? 360. How does mutton vary in composition from beef ? 361. How does it compare in food value with beef ? 362. How do lamb and mutton differ in composition ? 363. To what extent do the various cuts differ in composition ? 364. How do the more ex- pensive cuts of lamb compare in nutritive value with the less expensive cuts ? 365. How does pork differ in composition from other meats ? 366. Give the general composition of ham. 367. Give the composition and nutritive value of bacon. 368. How does bacon compare in food value with other meats ? 369. How does the character of the fat influence the composition and taste of the meat ? 370. What influences the texture or toughness of meats ? 371. How do cooked meats compare in composition with raw meats ? 372. To what extent are nutrients lost in the boiling of meats ? 373. What influence does the temperature of the water 334 HUMAN FOODS AND THEIR NUTRITIVE VALUE in which the meat is placed for cooking have upon the amount of nutrients extracted ? 374. To what is the shrinking of meats in cooking due ? 375. Of what does meat extract mainly consist ? 376. To what do beef extracts owe their flavor ? 377. What is their food value ? 378. What is their dietetic value ? 379. What is lard ? 380. How does it differ in composition from other fats ? 381. What is imparted to meats during the smoking process ? 382. Why is saltpeter used in the preservation of meats ? 383. Do vegetable foods contain nitrates and nitrites ? 384. How does poultry resemble and how differ in composition from other meat ? 385. Give the characteristics of sound poultry. 386. Give the general composition of fisli. 387. How does the flesh of different kinds of fish vary in composition? 388. What influence does salt- ing and preservation have upon composition ? 389. How do fish and meat compare in digestibihty? 390. How does the mineral matter and phosphate content of fish compare with that of other foods? 391. What are the main nutrients in oysters? 392. Give the general food value of oysters. 393. What is meant by the fatten- ing of oysters ? 394. What effect does the character of the water used in fattening have upon the sanitary value ? 395. Give the general composition of the egg. 396. How do different parts of the egg differ in composition ? 397. How does the egg differ in composi- tion from the potato ? 398. Is color an index to the composition of the egg ? 399. What effect does cooking have upon tlie compo- sition of the egg? 400. What factors influence the flavor of eggs ? 401. How do different ways of cooking affect tlie digestibility? 402. Under what conditions can eggs be used economically in the dietary? 403. Why should eggs be purchased and sold by weight? 404. How do canned meats differ in composition from fresh meats? 405. How do the nutrients of canned meats compare in cost with those of fresh meat? 406. What are the advantages of canned meats over fresh meats? 407. What are some of the materials used in the preservation of meats ? REVIEW QUESTIONS 335 CHAPTER IX Cereals 408. How are the cereals milled? 409. What are the cereals most commonly used for food purposes? 410. Give the general composition of cereals as a class. 411. What are the main nutri- ents in corn preparations? 412. What influence does the more complete removal of the bran and germ of corn have upon its diges- tibility? 413. How does the cost of nutrients in corn compare with other foods? 414. Why is corn alone not suitable for bread- making purposes ? 415. Why should corn be combined in a ration with foods mediumly rich in protein? 416. What change takes place in corn meal from long storage? 417. Give the characteris- tics and composition of oat preparations. 418. How does removal of the oat hull affect the composition of the product? 479. To what extent do the various oat preparations on the market differ in composition and food value? 420. Do oats contain any special alkaloidal or stimulating principle? 421. Why should oatmeal receive longer and more thorough cooking than many other foods? 422. To what extent are the nutrients in oatmeal digested? 423. How do wheat preparations differ in general composition from corn and oat preparations? 424. What influence upon the composition of the wheat breakfast foods has partial or complete removal of the bran ? 425. What is the effect upon their digesti- bility and nutritive value? 426. What are the special diabetic flours, and how are they prepared? 427. What are the wheat mid- dhngs breakfast foods, and how do they compare in digestibility and food value with bread? 428. How do they differ mechanically? 429. How does barley differ from wheat in general composition? 430. What is barley water, and what nutritive material does it contain? 431. What cereal does rice resemble in composition? 432. With what food materials should rice be combined to make a balanced ration? 433. What can you say as to comparative ease 336 HUMAN FOODS AND THEIR NUTRITIVE VALUE and completeness of digestibility of rice? 43/;. Why are cereals valuable in the ration? 435. In what way do they take a me- chanical part in digestion? 436. What are predigested breakfast foods? 437. How would you determine the general nutritive value of a breakfast food, knowing the kind of cereal from which it was prepared? 438. To what extent are cereals modified or changed in composition by cooking? 439. To what extent are the nutrients of cereal foods digested and absorbed by the body? 440. To what ex- tent do the cereals supply the body with mineral matter? 441. How does the phosphate content of cereals compare with that of meats and milk? CHAPTER X Wheat Flour 442. Why is wheat flour especially adapted to bread-making pur- poses? 443. To what extent may wheat vary in protein content? 444. What are spring wheats ? 445. What are winter wheats ? 446. Give the general characteristics of each. 447. What are gluti- nous wheats? 448. What are starchy wheats? 449. Name the different proteids in wheat flour. 450. About how much starch does wheat flour contain? 451. What other carbohydrates are also pres- ent? 452. What is the roller process of flour milling? 453. What is meant by the first break? 454. How are the different products of the wheat kernel separated? 455. What is meant by middlings flour? 456. What is break flour? 457. What is patent flour? 458. Name the high grade flours. 459. Name the low grade flours. 460. How are the impurities removed from wheat flour? 461. What per cent of the wheat kernel is returned as flour? As offals ? 462. What becomes of the wheat germ during milling? 463. What sized bolting cloths are used in milling? 464. What is graham flour? 465. How does it differ in mechanical and chemical com- position from white flour ? 466. What is entire wheat flour? 467. How does it differ in physical and chemical composition fro.ai REVIEW QUESTIONS 337 white flour? 468. What effect has the I'efining of flour upon the ash content? 469. How do low and high grade flours diff'er in chemical composition? 470. How do the wheat offals differ in composition from the flour? 471. What are the factors which influence the com- position of flours ? 472. What effect does storage have upon the bread-making value of flour? 473. What change takes place when new wheat is stored in an elevator? 474. What is durum wheat flour, and how does it differ from other flour? 475. What gives flour its color? 476. Why is color an index of grade? 477. How is the color of a flour determined ? 478. How do flours differ in granula- tion? 479. How does the granulation affect the physical properties of flour? 480. How is the granulation of flour approximately deter- mined? 481. How is the absorptive capacity of a flour determined ? 482. What factors cause a variation in the capacity of flours to absorb water? 483. Give the characteristics of a good gluten. 484. What causes unsound flours? 485. How is the bread-making value of a flour determined ? 486. How are flours bleached ? 487. How does bleaching affect the chemical composition of flour ? 488. What influence does bleaching have upon bread- making value? 489. Traces of what compounds are formed during bleaching ? 490. Are these compounds injurious to health ? 491. What effect does bleaching have upon the color of fiber and debris particles in flour? 492. Is it possible to bleach low grade flours and cause them to resemble high grade flours? 493. Are flours usually adulterated ? 494. Why ? 495. How would mineral adulterants be detected ? 496. How would the presence of other cereals be detected ? 497. How does flour compare in nutritive value with other foods ? 498. How does the cost of flour compare with that of other foods ? 499. What causes flours to vary so in bread-making value ? 500. Why may flours produced from the same type of wheat vary slightly in character from year to year ? 501. What relationship exists b.etween the nutritive and bread- making value of a flour? 338 HUMAN FOODS AND THEIR NUTRITIVE VALUE CHAPTER XI Bread and Bread Making 502. Define leavened and unleavened bread. 503. Why is yeast used in bread making ? 504. Give the characteristics of a good loaf of bread. 505. Why is flour used for bread making purposes? 506. Name the eight chemical changes that take place during bread making. 507. To what extent do losses in dry matter occur during bread making ? 508. What compounds suffer losses during bread making? 509. What is yeast ? 510. What chemical changes does it produce ? 511. What becomes of these products during bread making ? 512. How is compressed yeast made ? 513. What part does the alcohol take in bread making? 514. What temperature is reached in the interior of the loaf during bread making ? 515. Through what chemical changes does starch pass during bread making? 516. To what extent are soluble carbohydrates formed? 517. In what way is starch acted upon mechanically? 518. Explain the structure of the starch grains in flour and in dough after they have been acted upon by the yeast ferments. 519. To what extent are acids produced in bread making? 520. What becomes of the acids formed? 521. How may the acids thus developed affect the properties of other chemical compounds ? 522. To what extent are volatile carbon compounds, other than carbon dioxid and alcohol, liberated during bread making ? 523. What changes occur to the various proteids during the process of bread making ? 524. Why do flours vary in quality of gluten ? 525. To what extent do losses of nitrogen occur during bread making? 526. How much of the total nitrogen of flour is present as proteids ? 527. How is the fat of flour affected during the process of bread making? 528. What effect does the addition of 10 per cent of wheat starch to flour have upon the size of the loaf ? 529. What effect does the addition of 10 per cent of wheat gluten to flour have upon the size of the loaf? 530. What relationship exists between gluten con- tent and capacity of a flour to absorb water? 531 . C/ne the general REVIEW QUESTIONS 339 composition of bread. 532. What factors influence its composition? 533. What effect does the use of slcim milk and lard in bread making have upon composition? 534. How does the temperature of the flour influence the bread-making process? 535. Why is it necessary to vary the process of bread making in order to get the best results with different kinds of flour? 536. To what extent are the nutrients of bread digested? 537. How does graham bread compare in digestibility with white bread? 538. How do graham and entire wheat breads compare in nutritive value with white bread? 539. What value do graham and entire wheat breads have in the dietary? 540. Why is white bread generally preferable in the dietary of the laboring man? 541. How do graham and entire wheat flours compare in chemical composition with white flour? 542. How do they compare in mechanical composition? 543. To what is the difference in digestibility supposed to be due ? 544. Are graham and entire wheat breads necessary in a ration as a source of mineral elements? 545. What is the main difference in composition between old and new bread? 546. How do different kinds of bread made from the same flour compare in composition and nutritive value? 447. How does toast differ in composition from bread ? 548. What influence does toasting have upon digestibility? 549. What is gained by toasting bread? 550. How does bread compare in nutritive value With other cereal foods? 551. How does bread compare in nutritive value with animal foods? CHAPTER XII Baking Powders 552. What is a baking powder? 553. What are the two kinds of materials which baking powders contain ? 554. Name the differ- ent types of baking powders. 555. How does baking powder differ in its action from yeast? 556. What are the cream of tartar baking powders? 557. What is the nature of the residue which they leave? 558. What are the phosphate baking powders? 559. What is the 340 HUMAN FOODS AND THEIR NUTRITIVE VALUE nature of the residue which they leave? 560. Why is the mineral phosphate not considered equally valuable with that naturally present in foods? 561. What are the alum baking powders? 562. What residue is left from the alum powders? 563. Which of the three classes of baking powders is considered the least objectionable? 564. Why is a new baking powder preferable to one that has been kept a long time? 565. Why should baking powders be kept in tin cans, and not in paper? 566. Why are fillers used in the manufac- ture of baking powders? 567. How may a baking powder be pre- pared at home? 568. How does such a baking powder compare in cost and efficiency with those purchased in the market ? CHAPTER XIII Vinegars, Spices, and Coxdiiients 569. What is vinegar? 570. How is it made? 571. Give the three chemical changes that take place in its preparation. 572. Why is air necessary in the last stage of the process? 573. What ferments take part in the production of vinegar? 574. What is malt vinegar? 575. What materials other than apples can be used in the prepa- ration of vinegar? 576. Give the characteristics of a good vinegar. 577. In what ways are vinegars adulterated? 578. What food value has vinegar? 579. Why should vinegars not be stored in metalware? 580. What dietetic value has vinegar? 581. To what materials do the spices owe their value? 582. What is pepper? 583. What is the difference between white and black pepper? 584. What com- pounds give pepper its characteristics? 585. How are peppers adul- terated? 586. What is mustard? 587. Give its general composition. 588. How is it adulterated? 589. What is ginger? 590. How is it prepared for the market? 591. Give its genera] composition. 592. What is cinnamon? 593. What is cassia? 594. What gives these their taste and flavor? 595. What are cloves? 596. Howare they prepared? 597. What is mace? 598. What is nutmeg? REVIEW QUESTIONS 34T 599. Do the spices have any food vakie? 600. What is their dietetic value? 601. Why is excessive use of some of the spices objection- able? CHAPTER XIV Tea, Coffee, Chocolate, and Cocoa 602. What is tea? Name the two plants from which it is ob- tained, the countries where each grows best, and the number of flushes each yields. 603. Upon what does the quality and grade of tea depend? 604. Give differences in the preparation and composi- tion of green and black teas. 605. The characteristic flavor of tea is imparted by what compound? 606. To what compound are its pecuHar physiological properties due? 607. What can you say of the protein in tea as to amount and food value? 608. Why should tea ^ especially green tea — be infused for a very short time, never boiled? 609. What effect has tannin upon the digestion of proteids? 610. What three points are considered in judging a tea? 611. What is the most common form of tea adulteration? 612. Describe the coffee plant and fruit, and its method of preparation for market. 613. What is the difference in the chemical composition of tea and coffee? 614. Name the characteristic alkaloid of coffee. How does it compare with theine? 615. Why may coffee not be considered a food? 616. Tell different ways in which coffee may be adulterated. 617. Which is more commonly practiced, tea or coffee adulteration? Why? 618. How may real coffee be distinguished from chicory? Why? 619. Name the three kinds of coffee in general use. Give distinguishing features of each. Which is usu- ally considered best? 620. From what are cocoa and chocolate obtained? 621. Give the two methods of preparing cocoa. 622. What alltaloid similar to the theine and caffeine of tea and coffee is present in cocoa and chocolate ? 623. What is the difference in preparation of cocoa and chocolate ? 624. What are cereal coffee- substitutes? 625. What nutritive value have they? 626. How do 342 HUMAN FOODS AND THEIR NUTRITIVE VALUE they differ in composition from coffee? 627. To what extent does cocoa add to the nutritive value of a ration? 628. What is plain chocolate? 629. Why do chocolate preparations vary so widely in composition? 630. What treatment is given to the cocoa bean in its preparation for commerce? 631. What treatment is some-' times given to prevent separation of the cocoa fat? 632. In what ways may cocoa and chocolate preparations be adulter- ated? CHAPTER XV Digestibility of Foods 633. Define the term nutrient. 634. Do all the nutrients of food have the same degree of digestibility? 635. What is a diges- tion coefficient? 636. How is the digestibility of a food deter- mined? 637. What volatile products are formed during the diges- tion of food? 638. Define digestible protein; digestible carbohy- drates, digestible fat. 639. What is the available energy of a ration ? 640. How is it determined? 641. How do the nutrients, pro- tein, fat, and carbohybrates, compare as to available energy? 642. Why is it necessary to consider the caloric value of a ration? 643. Is the protein molecule as completely oxidized in the body as starch or fat? 644. What residue is left from the digestion of protein? 645. What part do the soluble ferments take in diges- tion? 646. To what extent are the nutrients of animal foods di- gested? 647. Which nutrient, protein or fat, is the most completely digested? 648. How do vegetable foods compare in digestibility with animal foods? 649. What effect does cellulose have upon digestibility? 650. Which of the nutrients of vegetables, protein or carbohydrates, is more completely digested? 651. What mechani- cal value may cellulose have in a ration? 652. Why must bulk be considered in a ration, as well as nutrient content? 653. Name the eight most important factors influencing the digestibilitv of foods. 654. To what extent does the combination of foods affect REVIICW QUESTIONS 343 the digestibility of the nutrients? 655. Why does a mixed ration give better results than when only a single food is used? 656. How does the amount consumed affect the completeness of the digestive process? 657. To what extent does the method of preparing food affect digestibility? 658. What is gained, so far as digestibility is concerned, by the cooking of foods? 659. To what extent does the mechanical condition of food affect its digestibility? 660. Why is it desirable to have some coarsely granulated foods in a ration ? 66i. Why should the ration not be composed exclusively of finely granulated foods ? 662. Why is some coarsely granulated food more essential in the dietary of the sedentary than in the dietary of the laborer ? 663. How does palatability affect the digestive process ? 664. Do psychological processes in any way affect digestion? 665. What physiological properties do some foods possess ? 666. To what are these physiological properties due ? 667. To what extent is individuality a factor in digestion ? 668. To what extent does digestibility differ with individuals? 669. Why do some foods affect individuals in different ways ? 670. Why is it necessary that the quantity, quality, and character of the food should vary with different individuals? 671. In what different ways is the expression "digestibility of a food" used? 672. Why is it necessary to consider the digestibihty of food, as well as its composition ? 673. Does the digestibility of a food nec- essarily indicate the economic uses that will be made of it by the body? 674. How is it possible for one food containing 10 per cent of digestible protein, and other nutrients in hke amounts, to be more valuable than another food with the same per cent of digesti- ble protein and other nutrients? 675. How is it possible for one food to contain less total protein than another food and yet be more valuable from a nutritive point of view ? 676. Why is it necessary to consider the mechanical condition of a food and its combination with other foods, as well as its chemical composition? 677. What effect does lack of a good supply of air have upon the completeness of the digestion process ? 678. In what ways does the digestion of food resemble the combustion of fuel ? 679. What is gained by a 344 HUMAN FOODS AND THEIR NUTRITIVE VALUE study of the digestibility of foods ? 680. Wliy may two foods of the same general character give different results when used for nu- tritive purposes? CHAPTER XVI Comparative Cost and Value of Foods 681. To what extent do the nutritive value and the market price of foods vary ? 682. How is the value of one food expressed in terms of another food ? 683. How determine the amount of nutri- ents that can be procured in a food for a given sum of money ? 684. How compare the amounts of nutrients that can be procured in two foods for a given sum of money ? 685. How is it possible to determine approximately which of two foods is cheaper, when the price and composition of the foods are known ? 686. To what nutrient is preference usually given in assigning a value to a food ? 687. When the difference in this nutrient between two foods is small, then the preference is given to what nutrients ? 688. At ordinary prices, what are the cheapest vegetable foods ? 689.. What are among the cheapest animal foods ? 690. Why is it not possible to determine the value of a food absolutely from its composition and digestibility ? 691. Why is it necessary to consider the physical as well as the chemical composition of foods? 692. What propor- tion of the income of the laboring man is usually expended for food ? 693. What are the most expensive foods ? 694. What foods furnish the largest amount of nutrients at the least cost ? CHAPTER XVII DiETARv Studies 695. What is a dietary study? 696. How is a dietary study made ? 697. What is the value of the dietary study of a family ? 698. To what extent does the protein in the dietary range ? REVIEW QUESTIONS 345 699. Why is a scant amount of protein in a ration undesirable ? 700. Why IS an excess of protein in the ration undesirable ? 701. What are dietary standards ? 702. How are such standards obtained ? 703. Why is it desirable in a ration to secure the pro- tein and other nutrients from a variety rather than from a few foods ? 704. Why is it necessary to consider the caloric value of a ration? 705. How is this determined ? 706. What is a wide nutritive ratio? 707. What is a narrow nutritive ratio? 708. Why should the amount of nutrients consumed vary with the work performed? 709. How should the nutrients be apportioned among the meals? 710. What are some of the most common dietary errors? 711. What analogy exists between human and animal feeding? 712. What is gained by the rational feeding of both humans and animals? 713. What use can be made of the results of dietary studies for improvement of the dietary? 714. Why is it not pos- sible for animal foods to compete in economy with cereal and vege- table foods? 715. Is a well-balanced ration and one containing an ample supply of nutrients necessarily an expensive ration? 716. Show how it is possible for one family to spend less money for food than another family, and yet secure more digestible nutrients and energy. 717. What are some of the most erroneous ideas as to food values? 718. Why is it necessary to consider previously acquired food habits in the selection of foods? 719. In general, what portion of the nutrients of a ration should be derived from vegetable foods, and what portion from meats? 720. To what extent may a ration vary from the dietary standards? 721. Why are some inexpensive foods often exijensive when prepared for the table? 722. What are some of the ways in which the cost of a ration can be decreased without sacrificing nutritive value? 723. Why do different nationalities acquire distinct food habits ? 724. Why is it not possible to make sudden and radical changes in the dietary ? 725. Why is it not possible for a dietary which gives ample satis- faction for one class of people to be applied to another class with equal satisfaction? 726. What relationship exists between the die- tary of a nation and its physical development? 727. What rela- 346 HUMAN FOODS AND THEIR NUTRITIVE VALUE tionship exists between dietary habits and mental development and vigor? 728. Why is it unnecessary and undesirable to regulate absolutely the amount of nutrients consumed in the daily ration? 729. What is the general tendency as to quantity of food and amount of nutrients consumed? 730. Why do people of sedentary habits require a different dietary from those pursuing active, out-of- door occupations? CHAPTER XVIII Rational Feeding of Man 731. What IS the object of the rational feeding of man? 732. On what IS it based ? 733. How does it compare with the rational feed- ing ot animals? 734. What is a standard ration? 735. How is it determined? 736. To what extent may the nutrients of a ration vary from the standard? 737. How do you combine foods to form a balanced ration? 738. What foods are valuable for supplying protein? 739. What foods supply fats? 740. What foods are rich in carbohydrates? 741. What other requisites should a ration have in addition to supplying the necessary nutrients? 742. Why is it necessary to consider the caloric value of a ration? 743. If a ration contained an excess of carbohydrates and a scant amount of protein, how could It be improved? 744. How do you calculate the nutrients in a fraction of a pound of food? 745. Give the amounts of the common food materials, as potatoes, bread, butter, milk, and cheese, ordinarily combined to form a ration. 746. To what extent may foods differ in composition from the average analysis given? 747. What foods are subject to the greatest and what foods to the least variation? CHAPTER XIX Water 748. Why is water regarded as a food? 749. Does it enter chemically into the composition of plants? Of animals? 750. In REVIEW QUESTIONS 347 addition to serving as a food, why is water necessary for life pro- cesses? 751. In wliat ways may water be improved? 752. What are the most common forms of impurities? 753. What are the mineral impurities of water? 754. What is their source? 755. What effect do some of these minerals have upon the value of the water? 756. What causes some waters to dissolve limestone? 757. What are permanently hard waters? 758. To what is temporary hardness in water due? 759. What is the best way to remove mineral matter from water? 760. What are the organic impurities of water? 761. What are the sources of the organic impurities? 762. What change does the organic matter of water undergo? 763. What be- comes of the nitrogen of the organic matter? 764. What does the presence of nitrates in water indicate ? Nitrites? 765. What is the total soHd matter of a water, and how is it obtained ? 766. Define the terms free ammonia; albuminoid ammonia. 767. What does the presence of chlorine in a surface well water indicate? 768. Ex- plain natural purification of water. 769. Can natural purification always be relied upon ? 770. Why does the character of the drink- ing water affect health? 771. What diseases are mainly caused by impure drinking water? 772. With what materials in water are the disease-producing organisms associated? 773. Why should a water of questionable purity be boiled? 774. State how the boiling should be done, to be effective. 775. Why should boiled water receive further care in its storage? 776. What effect does improvement of the water supply of a city have upon the death rate? 777. How may connections between cesspools and surface well waters be traced? 778. What impurities do rain waters contain ? 779. Ex- plain the workings of the Pasteur and Berkefeld water filters. 780. Why must special attention be given to cleaning the water filter? 781. Explain the processes employed for the removal of mechanical impurities of water by sedimentation and the use of chem- icals. 782. Why should such purification be under the supervision of a chemist or bacteriologist? 783. What effect does freezing have upon the purity of water? 784. Why are precautions necessary in the use of ice for refrigeration? 785. What are mineral waters? 348 HUMAN FOODS AND THEIR NUTRITIVE VALUE 7S6. How are artificial mineral waters prepared? 787. What are the more common materials used in their preparation? 788. Why should mineral waters be extensively used only by the advice of a physician? 789. What are some of the materials used for softening water? 790. Which are the least objectionable of these materials? 791. Which are the most objectionable? 792. What can you say of the use of ammonia and ammonium carbonate for softening waters? 793. In washing clothing after contagious diseases, what materials may be used for disinfecting? 794. Why, in softening waters for household purposes, must caustic soda, potash, and bleach- ing powder be used with caution? 795. Why is it necessary to determine by trial the material most suitable for softening water? 796. What advantage, from a pecuniary point of view, results from the improvement of the water supply of a community? CHAPTER XX Food in its Relation to Household Sanitation and Storage 797. What are the compounds usually determined in a food analysis? 798. Does such an analysis necessarily indicate the presence of injurious compounds? 799. What are the sources of the injurious organic compounds in foods? 800. Why is it necessary to consider sanitary condition as well as chemical composition? 801. What are the sources of contamination of foods? 802. What is the object of the sanitary inspection of food? 803. How may flies carry germ diseases? 804. Why should food be protected from impure air and dust particles? 805. Why should places where vege- tables are stored be well ventilated? 806. How may the dirt ad- hering to vegetables be the carrier of germ diseases? 807. Why should the cellar in which food is stored be in a sanitary condition? 808. What effect does the cleaning of streets and improvement of the sanitation of cities have upon the death rate? 809. Name the three natural disinfectants, and e.xplain the action of each. REVIEW QUESTIONS 349 810. Why must dishes and utensils in which foods are placed be thoroughly cleaned? 811. Explain the principle of refrigeration. 812. What kind of ferment action may take place at a low tempera- ture? 813. Why is some ventilation necessary in refrigeration? 814. What effect does refrigeration have uj^on the composition of food? 815. What relationship exists between unsanitary con- dition of soils about dwellings and contamination of the food? 8i6. Why should special attention be given to the sanitary disposal of kitchen refuse? 817. Name the ways in which this can be ac- complished. 818. How may foods become contaminated through imperfect plumbing? 819. Mention the conditions ■ necessary in order to keep foods sanitary. REFERENCES The following list of references is given for the use of the student in case additional information is desired upon some of the subjects discussed in this work. The list is not intended as a complete bibliography of the subject of foods. The advanced student will find extended references in the Experiment Station Record and the various chemical, physiological, and bacteriological journals. 1. Snyder: The Chemistry of Plant and Animal Life. 2. IVIinnesota Experiment Station Bulletin No. 54: Human Food Investigations. 3. Cross and Bevans: Cellulose. 4. Wiley: Principles and' Practice of Agricultural Analysis, Vol. III. 5. Minnesota Experiment Station Bulletin No. 74: Human Food Investigations. 6. Parry' : The Chemistry of Essential Oils, etc. 7. U. S. Department of Agriculture, Farmers' Bulletin No. 142: Principles of Nutrition and Nutritive Value of Food. y 8. Mann: Chemistry of the Proteids. 9. Minnesota Experiment Station Bulletin No. 85 : Wheat and Flour Investigations. 10. Armsbv ■ Principles of Animal Nutrition. 11. Sher.man: Organic Analysis. 12. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 43 : Digestion Experiments with Potatoes and Eggs- 13. Unpublished results of author. 14. U. S. Department of Agriculture, Bureau of Animal Industry Bulletin No. 49 : Cold Curing of Cheese. 350 REFERENCES 351 15. WiLEV : Foods and Their Adulteration. 16. Minnesota Experiment Station Bulletin No. 63 : Miscellaneous Analyses. 17. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 13, Part 8 : Canned Vegetables. 18. Leach: Food Inspection and Analysis. 19. U. S. Department of Agriculture, Farmers' Bulletin No. 256: Preparation of Vegetables for the Table. 20. U. S. Department of Agriculture Year Book, 1905 : Fruit and its Uses as Food. 21. Handbook of Experiment Station Work, 1893. 7-22. U. S. Department of Agriculture, Division of Chemistry Bulletin No. 94 : Studies on Apples. 423. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 69 : Fruits and Fruit Products. 24. y. S. Department of Agriculture, Farmers' Bulletin No. 203 : Canned Fruits, Preserves, and Jellies. 25. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 27 : Sugar Beet Industry. 26. Sadtler : A Handbook of Industrial Organic Chemistry. 27. Minnesota Experiment Station Bulletin No. 86 : The Food Value of Sugar. The Digestive Action of Milk. 28. Hutchison : Food and Principles of Dietetics. 29. U. S. Department of Agriculture, Farmers' Bulletin No 93 : Sugar as Food. 30. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 252 : Maple Sugar and Sirup. 31. U. S. Department of Agriculture, Bureau of Chemistry Bul- lAin No. 13, Part 6: Sugar, Molasses, Sirup, and Confec- tions. 32. U. S. Department of Agriculture, Farmers' Bulletin No. 121 ; Peas and Beans as Food. 33. ,U. S. Department of Agriculture, Farmers' Bulletin No. 122: Nuts as Food. ■'■ 34 Maine Experiment Station Bulletin No. 54: Nuts as Food. 352 HUMAN FOODS AND THEIR NUTRITIVE VALUE 35. California Experiment Station Bulletins Nos. 107 and 132: Investigations among Fruitarians. 36. U. S. Department of Agriculture, Farmers' Bulletin No. 74 . Milk as Food. 37. U. S. Department of Agriculture, Farmers' Bulletin No. 63 ; Care of Milk on the Farm. 38. V. S. Department of Agriculture, Farmers' Bulletin No. 149: Digestibility of Milk. 3'g. Russell ; Dairy Bacteriology. 40. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 13, Part I : Dairy Products. 41. U. S. Department of Agriculture, Farmers' Bulletin No. 131 : Household Tests for Detection of Oleomargarine and Reno- vated Butter. 42. U. S. Department of Agriculture, Bureau of Animal Industry Bulletin No 61 : Relation of Bacteria to Flavor of Cheddar Cheese. 43. Minnesota Experiment Station Bulletin No. 92 : The Digesti- bility and Nutritive Value of Cottage Cheese, etc. 44. Lawes and Gilbert: Experiments with Animals. 45. U. S. Department of Agriculture, Farmers' Bulletin No. 34: Meats, Composition and Cooking. 46. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 13, Part 7 : Lard and Lard Adulterants. 47. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 193 : Cooking of Meats as Affecting Digestibilitv. 48. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 141 : Experiments on Losses in Cooking Meats. See also Office of Experiment Stations Bulletin No. 102 : Losses in Cooking Meats. 49. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 66 : Physiological Effect of Creatin and Creatinin. 50. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 162 ; The Influence of Cooking upon the Nutri- tive Value of Meats. REFERENCES 353 51. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 13, Part 10: Preserved Meats. 52. Richardson, W. D.. Journal of the American Chemical Society, December, 1907: The Occurrence of Nitrates in Vegetable Foods, in Cured Meats, and Elsewhere. 53. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 182 : Poultry as Food. 54. U. S. Department of Agriculture, Farmers' Bulletin No. 85 : Fish as Food. 55. U. S. Department of Agriculture, Farmers' Bulletin, Experiment Station Work : Digestibility of Fish and Poultry. 56. U. S. Department of Agriculture, Farmers' Bulletin No. 249 : Cereal Breakfast Foods. 57. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 50: Composition of Maize. 58. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 305 : Gluten Flour and Similar Foods. 59. Hammerston : Physiological Chemistry. 60. Edgar : The Wheat Berry. 61. Minnesota Experiment Station Bulletin No. go : Composition and Value of Grains. 62. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 10 1 : Bread and Bread Making. 63. U. S. Department of Agriculture. Office of Experiment Stations Bulletin No. 156: Digestibility and Nutritive Value of Bread and Macaroni Flour. 64. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 67 : Bread and Bread Making. 65. University of Nebraska Bulletin No. 102 : The Effect of Bleach- ing upon the Quality of Wheat Flour. 66. Snyder: Wheat Flour and Bread. 67. U. S. Department of Agriculture, Office of Experiment Station? Bulletin No. 126: Bread and Bread Making. 68. Lawes axd Gilbert : Experiments on Some Points in the Composition of the Wheat Grain, of the Product in the Mill and Bread. 2 A 354 HUMAN FOODS AND THEIR NUTRITIVE VALUE 69. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 13, Part 5 : Baking Powders. 70. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 13, Part 2 : Spices and Condiments. 71. Food Standards : U. S. Department of Agriculture. See Annual Reports of the Association of Official Agricultural Chemists. 72. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 21 : Methods and Results of Investigations on the Chemistry and Economy of Foods. 73. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. 13, Part 7 : Tea, Coffee, and Cocoa Preparations. 74. The Respiration Calorimeter: Year-boolc U. S. Department of Agriculture, 1904. 75. Year Boole U. S. Department of Agriculture, 1902 : Cost of Food as Related to its Nutritive Value. 76. See v. S. Department of Agriculture, Office of E.xperiment Stations Bulletins Nos. 82, 71, 129, Ii5, 37, 55, 150. See also other bulletins of the Office of Experiment Stations. J. 77. Chittenden : Physiological Economy in Nutrition. 78. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 98 : Effect cf Severe and Prolonged Muscular Work on Food Consumption. 79. Henry: Feeds and Feeding. 80. U. S. Department of Agriculture, Office of Experiment Stations : Dietary Studies in Chicago Bulletin No. 55. 81. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 116: Dietary Studies in New York City. 82. U. S. Department of Agriculture, Farmers' Bulletin No. 119: Banana Flour. 83. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 159: Digest of Japanese Investigations on the Nutrition of Man. 84. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 150: Dietary Studies at the Government Hospi- tal for the Insane, Washington, D.C. REFERENCES 355 85. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 149: Studies on the Food of Maine Lumbermen. 86. U. S. Department of Agriculture, Office of Experiment Stations Bulletin No. 143 : Studies on the Digestibility and Nutritive Value of Bread at the Maine Experiment Station. 87. U. S. Department of Agriculture, Office of Experiment Stations, Experiment Station Work, Vol. Ill : Wells and Pure Water. 88. U. S. Department of Agriculture, Farmers' Bulletin No. 88: Pure Water on the Farm. 89. Mineral Impurities in Water. See various bulletins of the Cali- fornia and New Mexico Agricultural Experiment Stations. 90. Mason : Examination of Water. 91. Department of the Interior, U. S. Geological Survey: The Quality of Surface Waters in Minnesota. 92. FuERTES : Water and Public Health. 93. U. S. Department of Agriculture, Farmers' Bulletin No. 124: Distilled Drinking Water. 94. TuRNEAURE AND RusSELL : Public Water SuppUes. 95. Vaughan AND Now: Ptomains and Lcucomains. 96. U. S. Department of Agriculture, Bureau of Entomology, Circular No. 71 : House Flies. Ellen H. Richards and S. Maria Elliott: The Chem- istry of Cooking and Cleaning. 98. Dr. Woods Hutchinson, Saturday Evening Post, 1908: The Real Angels of the House. 99. Harrington : Practical Hygiene. 100. Price : Handbook of Sanitation. 97- INDEX Air, infection from impure, 2S7. pure, disinfectant, 290. Albuminoids, 23. Alkaloids, 24. Allspice, 202. Almonds, 77. Alum baking powder, iSS. Amids and Amines, 23. Animal and vegetable foods, economy of, 250. Animal foods, digestibility of, 220. Apparatus used in experiments, 301. Apples, 49- pectose from, 307. Ash, of foods, 4. elements of plants, 5. Asparagus, 43. Available energy, 217. nutrients, 216. Bacteria in food, 32. Baking powder, composition of, 186. cream of tartar, 187. phosphates, 189. alum, 189. inspection of, 191. fillers, 191. home-made, 191. testing for alum, 315. testing for ammonia, 316. testing for phosphoric acid, 316. Baking tests, 153-314. Barley preparations, 128. Beans, composition, 71. digestibility, 72. removal of skins, 72. string, 73. use of, in dietary, 74. Beef, 1 01. extracts, no. Beets, 41. Beverages, composition, 213. Bleaching of flour, 155. Bolting cloth, 138. Bread and bread making, 158-185. leavened and unleavened bread, 158. chemical changes during making, 159- losses during bread making, i6o. production of carbon dioxide, 163- production of alcohol, 163. production of soluble carbohy- drates, 165. production of acids, 166. production of volatile compounds, 167. production of volatile nitrogenous compounds, 172. wheat proteids, part taken by, 169. oxidation of fat, 173. starch, influence of, addition of, 173. composition of bread, 174. temperature of flour, 176. use of skim milk, 176. process of bread making, 177. digestibility of bread, 178. graham bread, use in the dietary, 179. white and graham bread compared, 180. mineral content of, 182. 357 3S8 INDEX new and old, 183. action of heat on, 184. different kinds of, 184. Breakfast foods, 1 21-132. Broth, 109. Butter, composition, 91. digestibility, 91. adulteration, 92. coloring, 92. renovated, 92. water in, 305. Buttermilk, 88~ Cabbage, 41. Candies, 69. Canned meats, iiS. vegetables, 46. peas, 75. Carbohydrates defined, S. Carrots, 40. Cauliflower, 41, Cellars, storage of food in, 283. Cellulose and properties, 8. Cereals, 1 21-132. preparation of, 121. cost of, 121. value of, 131. use of, in dietary, 131. corn preparations, 122. oat preparations, 124. wheat preparations, 126. barley preparations, 12S. rice preparations, 129. predigested, 130. phosphates in, 131. mineral matters of, 131. coffees, 210. Cesspools, 289. Cheese, 92-96. general composition, 92. digestibility, 93. use of, in dietary, 94. cottage, 95. different kinds of, Q5. adulteration, 96. Chemical changes during cooking, 27- Chemicals, use of, in preparation of foods permitted, ^6. Chestnuts, 76. Chicory, detection in coffee, 319. Chocolate, 212. adulteration of, 213. Cinnamon and cassia, 201. Cloves, 201. Coal tar dyes, testing for, 308. Cocoa, 210. Cocoanuts, 77. Coffee, composition of, 207. detection of chicory in, 319. glazing of, 208. substitutes, cereal, 210. types of, 2og. Combustion of foods, 6. Cooking, changes during, 27, chemical, 27—30. physical, 30-32. bacteriological, 32. Corn, sweet, 41. preparations, 122. Cream, 87. Cream of tartar, 187. Crude fiber of foods, 9. Crude protein, 21. Cucumbers, 42. Dairy products, 80-97. use of, in dietary, 96. Dextrose, 64. Dietary standards, 245. Dietary studies, 244-260. object of, 244. mixed, desirable, 250. of families compared, 253. in public institutions, 259. Digestibility of foods, 214. of animal foods, 220. of vegetable foods, 222. Digestion, combination of foods, 223. factors influencing, 223. INDEX 359 amount of food, 224. method of preparation of food, 225. mechanical condition of foods, 226. psychological factors, 230. individuality, 229. Digestion and health, 219. Dishcloth, unclean, 292. Disinfectants, 281, 289, 295. Drying of foods, 2. Dry matter, ^. Egg plant, 44. Eggs, 114-118. composition, 114. digestibility, 116. cooking of, 116. use of, in dietary, 117. Elements in foods, 7. Energy, available, 217. Energy value of rations, 246. Entire wheat, 145. Essential oils, 15. occurrence, 15. composition of, 16. food value, 16. Esthetic value of foods, ^6. Fat, occurrence in food, 12. composition, 13, physical properties, 14. food value, 14. individual fats, 14. oxidation of, during bread making, 173- Ferments, soluble, 34. insoluble, 34. Figs, 54- Fish, 113. Flavoring extracts, 56. Flavors, composition of, 48. occurrence of, 49. food value, 49. Flies, contamination of food by, 286, 295- Foods, 215. digestibility of, 215. mechanical condition of, 226. palatability of, 22S. physiological properties of, 228. ash of, 4. predigested, 130. sodium chloride in, 4, cost of, 231. market price and nutritive value, 231-234- composition of, 234-263. comparative nutritive value, 231. economy of production, 250, habits, 250, notions, 252. relation to mental and physical vigor, 258. amount consumed, 262. , —^ip j^irio us compounds in, 284. ^Si^tar^ination of, 284, 292. saaftary inspection of, 286. storage in cellars, 288. infection from impure air, 287. utensils for storage, 291. raw, 27. cheap and expensive, 252. Fruits, composition of, 48. canned, 54. dried, 54. canned and adulterated, 55. Fruit extracts, 56. Fruit flavors, 55. Ginger, 200. Gliadin, 314. Gluten, addition of, to flour, 173. moist and dry, 314, Gluten properties of flour, 151. Graham bread, 179. use in dietary, rSo. Graham flour, 144. Grape fruit, 51. Grapes, 53. 360 INDEX Heat, action on foods, 30. Hickory nuts, 77. Honey, 68. Ice, 279. Inspection of food, 2S6. Inversion of sugar, 64. Kitchen refuse, Koumiss, 88. 294. Laboratory practice, 299. Lard, 106. substitutes, 107. Legumes, 71-76. Lemon extract, testing, 307. Lemons, 51. acidity of, 305. Lettuce, 42. Macaroni flour, 148. Mace, 202. Malted foods, 121. Maple sugar, 62. Meals, number of, per day, 248. Measuring, .directions for, 302. Meat broth, 109. Meats, 98-120. general composition, 98. proteids of, 99. fat of, 100. water of, 98. texture of, 107. cooking of, influence of, on com- position, 108. extractive materials, no. smoked. III. boric acid in, 312. saltpeter in, in. canned, 118. Melons, 43. Microscope, use of, 304. Milk, importance in dietary, 80. general composition, 80. souring of, 86. condensed, 87. digestibility, 81. sanitary condition, 82. certified milk, 84. pasteurized, 84. color of, 85. preservatives in, 86. goat's, 88. human, 89. adulteration of, 89, prepared, 88. formaldehyde in, 310. Mineral matter, 4. in ration, 5. Mineral waters, 279. Miscellaneous compounds, 16. Mixed nitrogenous compounds, 25. Mixed non-nitrogenous compounds, 16. Moisture content of foods, variations in, 1 . Moisture in foods, how determined, 2. Molasses, 65. Mustard, 199. testing for turmeric, 318. Mutton, 103. Nitrates in foods, 45. Nitrites in foods, in. Nitrogen free extract, n. defined, n. composition, 12. how determined, 12. variable character of, 12. Nitrogenous compounds, 17. general composition, 17. Non-nitrogenous compounds, classi- fication of, 7. Nutmeg, 202. Nutrients, available, 216. Nutritive value of nitrogenous com- pounds, 16. starch, 9. sugar, II. nitrogen free extiact, 11. fat, 12. INDEX 361 protein, 19, amids, 23. Nuts, 76-79. use of, in dietary, 78. Oat preparations, 124. Oleomargarine, 92. detecting, 310. Olive oil, testing, 308. Olives, 54. Onions, 42. Oranges, 50. Organic acids, 15. occurrence in foods, 15. influence on digestion, 15. use in plant economy, 15. production during germination, 15. Organic compounds, classification of, 7-_ Organic matter, 6. Oysters, 114. Palatability of food, 228. Parsnips, 40. Peaches, 53. Peanuts, 76. fat from, 309. Peas, 74. canned, 75. Pectose substances, 11. Pepper, 198. Phosphate baking powders, i8g. Physical changes during cooking, 30. Physiological properties of foods, 228. Pistachio, 77. Plumbing, sanitary, 297. Plums, 53. Pork, 104. Potatoes, 37. composition, 39. digestibility, 38. nutritive value, 38. sweet, 39. Poultry, 112. Predigested foods, 130. Protein, composition of,' 19. properties of, 19. combinations of, 20. types of, 20. crude, 21. food value of, 22. amount of, in ration, 246. Psychological factors in digestion, 230. Pumpkins, 45. Rational feeding of man, 261-267. Rations, wide and narrow, 245. standard, 261. object of, 261. examples of, 264. requisites of, 266. protein requirements of, 246. energy value of, 246. References, 350. Refrigeration, 292. Refuse, disposal of, 294. Renovated butter, 92. Review questions, 323. Rice preparations, 129. Saccharine, 70. Saltpeter in meats, 11 1. Sanitary condition of vegetables, 45. Sanitary inspection of food, 2 So. Sausage, iii. Sodium chloride in foods, 5. Soil, sanitary condition of, 294. Spices, 212. Spinach, 42. Squash, 45. Starch, 9. occurrence, 9. composition, 9. properties, 10. food value, 10. influence of heat on, 10. Strawberries, 52. Sugar, defined, 11. beet, 58. cane, 58. commercial grades, 58. manufacture of, 59. 362 INDEX sulphur in, 59. digestibility of, 59. value of, in dietary, 61, adulteration of, 63. maple, 62. dextrose, 64. Sunlight as a disinfectant, 290. Sweet potatoes, 39. Syrups, 66. sorghum, 66. Tea, 203-206. black, 203. green, 204. composition of, 214. judging of, 205. adulteration of, 206. physiological properties of 206. examination of leaves, 318. Toast, 184. Tomatoes, 43. Underfed families, 251. \''anilla extract, testing, 307. Veal, 102. Vegetable foods, 222. Vegetables, 37-47. edible portion, 47. canned, 46. sanitary condition of, 45. digestibility of, 222. Vinegar, 193-197. preparation of, 193. different kinds of, 19s. adulteration of, 196. solids, 316. specific gravity, 317. acidity, 317. Volatile matter, 6. Water, drinking, 268-283. importance, 268. impurities in, 269. mineral impurities, 270. organic impurities, 271. purification of, 272-27S. analysis, 271. and typhoid fever, 273. improvement of, 276. boiling of, 276. filtration of, 277. distillation of, 278. materials for softening water, 280, testing purity of, 320. Water in foods, 1. how determined, 1. Water supply, economic value, 282. Waters, mineral, 279. Weighing, directions for, 302. Wheat cereal preparations, 126. W^heat flour, 133. spring and winter wheat flour, 133. starchy and glutenous, 135. composition of, 136. process of milling, 136-140. patent, 142. grades of, 142. composition of, 143. ash content, 145. graham, 145. entire wheat, 145. by-products, 146. aging and curing, 147. macaroni, 14S. color, 148. granulation, 149. capacity to absorb water, 150. gluten, properties of, 151. unsoundness of, 152. baking tests, 153. bleacliing of, 155. adulteration of, 156. nutritive value of, 157. water in, 304. ash in, 305. acidity of, 313. moist and dry gluten, 314. Yeast, action of, 161. compressed, 162. dry, 163. By harry SNYDER, B.S. Professor of Agricultural Chemistry, University of Minnesota, and Chemist of the Minnesota Agricultural Experiment Station The Chemistry of Plant and Animal Life Illustrated. Cloth. i2mo. 40b pages. $1.40 ; by mail, $i.jo "The language is, as it should be, plain and simple, free from all needless technicality, and the story thus told is of absorbing interest to every one, man or woman, boy or girl, who takes an intelligent in- terest in farm life." — 7Ae New England Partner. "Although the book is highly technical, it is put in popular form and made comprehensible from' the standpoint of the farmer; it deals largely with those questions which arise in his experience, and will prove an invaluable aid in countless directions." — The Farmer's Voice. Dairy Chemistry Illustrated, igo pages. $/.oo net; by mail, $i.ro "The book is a valuable one which any dairy farmer, or, indeed, any one handhng stock, may read with profit." — Rural A'eui Yorker. Soils and Fertilizers Third Edition. Illustrated, $1.2^ net ; by mail, $i.j8 A book which presents in a concise form the principles of soil fertihty and discusses all of the topics relating to soils as outlined by the Com- mittee on Methods of Teaching .-Xgriculture. It contains 350 pages, with illustrations, and treats of a great variety of subjects, such as Physical Properties of Soils ; Geological Formation, etc.; Nitrogen of the Soil and Air ; Farm Manures ; Commercial Fertilizers, several chapters ; Rotation of Crops ; Preparation of Soil for Crops, etc. THE MACMILLAN COMPANY 64-66 FIFTH AVENUE, NEW YOBK BOOKS ON AGRICULTURE On Selection of Land, etc. Thomas F. Hunt's How to Choose a Farm E. W. Hilgard's Soils : Their Formation, and Relations to Climate and Plant Growth Isaac P. Roberts' The F'armstead On Tillage, etc. F. H. King's The Soil Isaac P. Roberts' The Fertility of the Land . . Elwood Mead's Irrigation Institutions .... F. H. King's Irrigation and Drainage . . William E. Smythe's The ('onquest of Arid America Edward B. Voorhees' Fertilizers Edward B. Voorhees' Forage Crops .... H. Snyder's Chemistry of Plant and Animal Life . H. Snyder's Soils and Fertilizers. Third editiun . . L. H. Bailey's Principles of Agriculture . . W. C. Welborn's Elements of Agriculture, Southern and Western On Plant Diseases, etc. George Massee's Plant Diseases .... E. C. Lodeman's The Spraying of Plants . ... H. M. Ward's Disease in Plants (English) A. S. Packard's A Text-book on Entomology .... On Production of New Plants L. H. Bailey's Plant-Breeding . . L. H. Bailey's The Survival of the Unlike . . L. H. Bailey's The Evolution of our Native Fruits . . W. S. Harwood's New Creations in Plant Life . . . On Garden-Making L. H. Bailey's Practical Garden Book L. H. Bailey's Garden-Making L. H. Bailey's Vegetable-Gardening . . . . L. H. Bailey's Horticulturist's Rule Book .... L. H. Bailey's Forcing Book .... A- French's Book of Vegetables 75 net 4 CO net ' 50 net 50 net 50 net 25 net 50 net 50 net 25 net 50 net 25 net 25 net 25 net 75 net I 60 net I 25 net I 60 net 4 50 net I 25 net 2 00 net 2 00 net I 75 net I 00 net I 50 net I 50 net 75 net I 25 net I 75 net BOOKS ON AGRICULTURE— Cbn«naerf On Fruit-Growing, etc. L. H. Bailey's Nursery Book . $i 50 net L. H. Bailey's Fruit-Growing '5° "s' L. H. Bailey's The Pruning-Book I 50 net F. W. Card's Bush Fruits I 50 net On the Care of Live-stock Nelson S. Mayo's The Diseases of Animals '5° "^t W. H. Jordan's The Feeding of Animals I 50 net I. P. Roberts' The Horse i 25 net George C. Watson's Farm Poultry I 25 net On Dairy Work, Farm Chemistry, etc. Henry H. Wing's Milk and Its Products I 50 net C. M. Aikman's Milk I 25 net Harry Snyder's Dairy Chemistry . . I 00 net W. D. Frost's Laboratory Guide in Elementary Bacteriology . i 60 net J. G. Lipman's Bacteria and Country Life • 5° °^' Lincoln and Walton's Elementary Quantitative Chemi- cal Analysis '5° n^t On Economics and Organization Henry C. Taylor's Agricultural Economics i 25 net I. P. Roberts' The Farmer's Business Handbook ... i 25 net George T. Fairchild's Rural Wealth and Welfare . . 1 25 net S. E. Sparling's Business Organization i 25 net In the Citizen's Library. Includes a chapter on Farming L. H. Bailey's The State and the Farmer I 25 net On Everything Agricultural L. H. Bailey's Cyclopedia of American Agriculture To be complete in four royal 8vo volumes, with over 2000 illustrations Price of sets : Cloth, $ 20 net; half morocco, $ 32 net For further information as to any of the above, address the publishers, THE MACMILLAN COMPANY 64-66 FIFTH AVENUE, NEW YOKE Cyclopedia of American Agriculture Edited by L. H. BAILEY Of Cornell University, Editor of " Cyclopedia of American Horticulture," Author of " Plant Breeding," " Principles of Agriculture," etc. WITH loo FULL-PAGE PLATES AND MORE THAN 20OO ILLUS- TRATIONS IN THE TEXT— FOUR VOLUMES — THE SET: CLOIH, $20NET— HALF MOROCCO, J 32 NEI' — CARRIAGE EXTRA Volume I — Farms The Agricultural Regions — The Projecting of a Farm — The Soil Environment — The Atmosphere Environment. Volume II — Crops The Plant and Its Relations- — The Manufacture of Crop Products — North American Field Crops. Volume III — Animals The Animal audits Relations — The Manufacture of Animal Prod- ucts — North American Farm Animals. Volume IV — The Farm and the Community Economics — Social Questions — Organizations — History — Litera- ture, etc. " Indispensable to public and reference libraries . . . readily com- prehensible to any person of average education." — The Nation. "The completest existing thesaurus of up-to-date facts and opinions on modern agricultural methods. It is safe to say that many years must pass before it can be surpassed in comprehensiveness, accuracy, practical value, and mechanical excellence. It ought to be in every library in the country." — Record Herald, Chicago. PUBLISHED BY THE MACMILLAN COMPANY 64-66 FIFTH AVENUE, NEW YOEK