WHEAT FLOUR AND BEKAD 
 
 Snyder sJici Wooes 
 
Cornell University Library 
 
 TX 558.W5S67 
 
 Wheat flour and bread. 
 
 3 1924 003 564 790 
 
tVHEAT FLOUR AND BREAD 
 
 HARRY SNYDER, 
 
 Profess<or of Chetn'mtrti, Cnlh'iji' of A(/rlcidtnri% Unlrersily of Minnesota, 
 
 CHARLES D. WOODS, 
 
 Director iHnltn' AcjriciiUiirul I'li-jn-riinnit Station. 
 
 [Repkint fri«[ Yeakbook of Department of Agkicultuke for 1903.] 
 
Cornell University 
 Library 
 
 The original of tiiis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924003564790 
 
CONTENTS. 
 
 . Page. 
 
 Introduction '. 347 
 
 C'erealt^ used in bread making 348 
 
 The process of bread making '. 349 
 
 Losses of material in bread making 352 
 
 Tlie composition of. bread 353 
 
 Graham, entire wheat, and st'andard patent flours 354 
 
 The digestibility of bread .^ 358 
 
 The nutritive value of bread 361 
 
 Conclusion 361 
 
 III 
 
WHEAT FLOUR AND BREAD. 
 
 "By Harry Snyder, Professor of Chemistry, College of Agriculture, University of Minnesota, 
 and Charles D. Woods, Director Maine Agricultural Experiment Station. 
 
 INTRODUCTION. 
 
 By far the most important of the vegetable foods in the diet of the 
 American people are the cereals. From the results of some 200 dietary 
 studies, carried on in connection with the cooperative nutrition inves- 
 tigations of the Department of Agriculture among families in widely 
 varying circumstances in different parts of the country, it appears 
 that on an average the different kinds of cereal products together 
 comprised about 22 per cent of the total food and supplied 30 per 
 cent of the total protein, 7 per cent of the total fat, and nearly 55 
 per cent of the total carbohydrates in the diet. 
 
 The cereals in common use are wheat, oats, corn (maize), rye, rice, 
 barley, and buckwheat, the first three being in this country much 
 more important than the others. For the most part they are used in 
 the form of either flour or meal. If the latter term is interpreted 
 broadly it will include the so-called breakfast foods that have lately 
 come into extensive use, as most of them are little more than specially 
 prepared meals. Such foods afford a pleasing variety in the diet, and 
 because of special treatment in their manufacture, often including 
 partial cooking, somewhat simplify the problem of preparation for the 
 table. But of the various forms in which cereal products may be 
 prepared, that which has proved the most universally satisfactoi-y is 
 bread made from rather finely ground meal or flour, and among all 
 civilized people the art of bread making is highly developed. 
 
 For several years the nutrition investigations of the Department of 
 Agriculture, particularly those carried on at the Maine and Minnesota 
 experiment stations in cooperation with the Ofiice of Experiment Sta- 
 tions, have included studies of various problems connected with the 
 production of bread and the nutritive value of bread of different kinds. 
 So much has been accomplished in this work that it is believed possi- 
 ble now to draw some definite conclusions from the results obtained. 
 It is the purpose in the present article to consider briefly some of the 
 facts concerning the materials from which bread is made, the changes 
 and losses which occur in the making of bread, and the digestibility, 
 nutritive value, and economy of bread from different grades of wheat 
 flour. 
 
 347 
 
348 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 
 CEREALS USED IN BREAD JIAKING. 
 
 The simplest kind of bread nialting consists in mixing the meal or 
 flour with water and baking it, thus producing what is known as 
 unleavened bread, such as the "unleavened bread" of the Jews and 
 the common cracker, or, as called by the English, biscuit. Bread of 
 this nature is dry and hard and, unless baked in a very thin cake, is 
 difficult to masticate. Sometimes in making crackers a little fat 
 (shoi'tening), as butter or lard, is added, and in some kinds baking 
 powders are used to lighten them and improve the texture. The bread 
 most preferred, however, is that which has been raised, or leavened, 
 by producing in the dough a gas that will render it porous. Such 
 bread is light and moist and easy to masticate. A few words will be 
 appropriate here regarding the bread-making jjroDerties of the dif- 
 ferent cereals. 
 
 Meal or flour from any of the cereals may be used for unleavened 
 bread, but leavened bread can be made only from those which contain 
 gluten, a mixture of vegetable proteids which when moistened with 
 water becomes viscid, and is tenacious enough to confine the gas pro- 
 duced in the doughY* Most cereals, like barley, rice, oats, and corn, 
 some of which are very commonly made into forms of unleavened 
 bread, are deficient or wholly lacking in gluten, and hence can not be 
 used alone for making leavened bread. For the latter purpose rye 
 and wheat, which contain an abundance of gluten, are best fitted, 
 wheat being in this country by far the more commonly used. 
 
 Macai'oni, vermicelli, and other forms of Italian paste constitute a 
 very important class of foods made from wheat. These do not resem- 
 ble bread in form, though in food value and in use in the dietary 
 they are very similar to it. Flour paste or dough somewhat similar 
 to that used for crackers is prepared for making these materials, a 
 flour rich in gluten being mixed with water into a paste, which is cut 
 in various forms or pressed into rods, tubes, etc., and is then dried 
 rather than baked. For the finest of these materials a special kind of 
 wheat is preferred, a very hard sort, which has lately assumed impor- 
 tance in this country, and is known best as macaroni wheat. 
 
 The grain of rye is to some extent similar to that of wheat, but 
 difl'ers in some important features. It makes darker flour, and its 
 gluten has not the same elastic tenacious quality; hence the rye loaf 
 is not as light and well raised as that of wheat. Rye flour when used 
 alone produces the dark-colored bread which is extensively used in 
 European countries, in many of which it forms the staple article of 
 diet among the poor people, rye flour there being cheaper than wheat. 
 It is commonly regarded as inferior to wheat bread in flavor, but 
 approaches it closely in nutritive value. In the opinion of many 
 persons, rye flour mixed with a considerable proportion of wheat 
 flour makes a much better bread than rye flour alone, and such a 
 mixture is used to some extent in this country. 
 
WHEAT FLOUR AND BREAD. 349 
 
 THE PKOCESS OF BREAD MAKING. 
 
 Ill makin g unleavened br ead the flour is moistened and worked into 
 a stiff dough, which is then rolled, cut into various shapes, and baked, 
 forming a thin, brittle biscuit or cracker. ) The process of making 
 raised or leavened bread consists, in brief, in mixing the flour and 
 water in proper proportions for making a stiff dough, together with 
 some salt for seasoning and yeast (or other agent) for leavening. 
 The moistened gluten of the flour forms a viscid, elastic, tenacious 
 mass, which is thoroughly kneaded to distribute the yeast. The 
 dough is then kept in a warm place and the yeast begins to grow, or 
 "work," causing alcoholic fermentation with the production of carbon 
 dioxid gas, which expands the dough, or causes it to "rise," thus 
 rendering it porous. After the yeast has grown sufficientlj^, the 
 dough is baked in a hot oven, where further fermentation is stopped 
 by the destruction of the j'east by heat, which also causes the gas 
 to expand in the loaf and, in addition, generates steam. The gas and 
 steam inflate the tenacious dough and finally escape into the oven. 
 At the same time the gluten of the dough is hardened by heat, and 
 the mass remains porous and light, while the outer surface is dark- 
 ened and formed into a crust. 
 
 When the flour is of good quality, the dough well prepared, and 
 the bread properly baked, the loaf has certain definite characteristics. 
 Thus, it should be well raised and have a thin, flinty' crust, which is 
 not too dark in color nor too tough, but which cracks when broken. 
 The crumb, as the interior of the loaf is called, should be poi-ous, 
 elastic, and of uniform texture, without large holes, and should have 
 a good flavor and odor. 
 
 It has already been indicated that gluten is the ingredient of the 
 flour on which its bread-making properties chiefly depend. The 
 important thing is not entirely the quantity of gluten, however, but 
 more particularly its character. Two flours containing the same amounts 
 of carbohydrates and proteid compounds, when eon\'erted into bread 
 by exactly the same process, maj^ produce bread of entirely different 
 physical characteristics because of differences in the nature of the 
 gluten in the two samples. All gluten is composed of two bodies 
 called gliadin and glutenin, and the principal factor which determines 
 the character of the gluten is the proportion of gliadin to glutenin in 
 it. The gliadin, a sort of plant gelatin, is the material which binds 
 tlie flour particles together to form the dough, thus giving it tenacity 
 and adhesiveness; and the glutenin is the material to which the gliadin 
 adheres. If there is an excess of gliadin the dough is soft and sticky, 
 while if there is a deficiency it lacks in expansive powers. Many 
 flours containing a large amount of gluten and total proteid material, 
 and possessing a high nutritive value, do not yield bread of the best 
 
350 YEARBOOK OF THE DEPAKTMENT OF AGEIOULTUEE. 
 
 quality because of an imperfect gliadin-glutenin ratio. This question 
 is of much importance in the milling of wheats, especiallj' in the 
 blending of different types of wheat. At the Minnesota experiment 
 station considerable study has been made of this and other problems 
 regarding the bread-making properties of wheat. 
 
 Some of the Minnesota experiments were planned to test the question 
 whether it is the starch content or the gluten content that determines 
 the- bread-making quality of flour. In certain cases the proportion of 
 starch in a normal flour was increased 10 to 20 per cent by the addition 
 of wheat starch, while in others it was deci'eased to the same extent, 
 and in still others 10 to 20 per cent of corn flour was added to the 
 wheat flour. In all cases the bread made from the flours containing 
 increased or decreased quantities of starch was compared with that 
 made from a like quantity of the normal flour. In the experiments 
 in which the proportion of starch was increased bj- adding- either 
 wheat starch or corn flour there was practically no difference in either 
 the size or the appearance of the loaf as compared with that from 
 normal flour. The results of these tests, as well as of those made in 
 other countries, clearly indicate that it is the gluten rather than the 
 starch content that determines the bread-making properties of the 
 flour. 
 
 Similarly, little difference was observed between the bread from 
 normal flour and that from flour with the proportion of starch dimin- 
 ished. The proportion of starch was diminished, not by removing 
 starch from normal flour, but bj' adding gluten to it. These tests 
 likewise showed that it is not the starch content that determines the 
 bread-making quality of the flour. Thej^ also showed that there is a 
 limit beyond which it is inadvisable to increase the quantity of gluten 
 in flour in order to produce a large-sized loaf. An abnormally large 
 amount of gluten does not j'ield a correspondingly large loaf. 
 
 Experiments were also made to determine the relation between the 
 nature of the gluten and the character of the bread. This was done 
 by comparing bread from normal flour with that from other flour of 
 the same lot, but having part or all of its gliadin extracted. Dough 
 made from the latter was not sticky, but felt like puttj', and broke in 
 the same way. The yeast caused the mass to expand a little when first 
 placed in the oven; then the loaf broke apart at the top and decreased 
 in size. When baked it was less than half the size of that from the 
 same weight of normal flour, and decidedly inferior in other respects. 
 It was about as heavy as the same quantity of rubber. The removal 
 of part of the gliadin produced nearly the same effect as the extraction 
 of the whole of it, and even when an equal quantity of normal flour 
 was mixed with that from which part of the gliadin had been extracted 
 the bread was only slightly improved. Similar results were also 
 
WHEAT FLOUE AND BREAD. 351 
 
 obtained at the New Jersey station in experiments with flour from 
 which the gliadin had been extracted. From these experiments it is 
 evident that the bread -mailing properties of the flour depend upon the 
 nature of the gluten, as any alteration of the character of the gluten 
 or the proportion of its constituents in the flour has a strong influence 
 upon the character of the bread produced. On the other hand, when 
 the character of the gluten or the proportion of its constituents is 
 undisturbed a foreign proteid maj' be introduced without interfering 
 with the rising of the bread. Thus, in the experiments in which corn 
 flour was added, the proteid of the corn had no effect upon the power 
 of expansion of the normal flour. 
 
 In flour of the highest bread-making properties the two constituents, 
 gliadin and glutenin, are present in such proportions as to form a well- 
 balanced gluten. From the data at hand it would appear that for the 
 best results the proper proportion of gliadin to glutenin in hard-wheat 
 flour is about 65 to 35 in 100 parts. Occasionally the percentage of 
 gliadin may fall as low as 55. A large variation from this ratio has a 
 marked influence upon the character of the bread. Advantage is taken 
 ,of this fact in the milling of wheat when the blending of opposite 
 types, one with high and the other with low gliadin content, is resorted 
 to before grinding in order to improve the quality of the flour. 
 
 Flours of diilerent bread-making properties may also be improved 
 by blending after milling. At the Minnesota station experiments were 
 made by combining a hard-wheat flour that had a high gluten content, 
 but was relativeh' deficient in gliadin, with a soft-wheat flour that had 
 a lower gluten content, but whose gluten contained a high percentage 
 of gliadin, in such proportions that the ratio of gliadin to glutenin in 
 the blended flour was 64 to 36. The hard-wheat flour alone produced 
 as large a loaf as that from the blended flour, but the latter produced the 
 best loaf. The soft-wheat flour produced a soft, sticky dough that 
 expanded while rising but collapsed during the baking, so that the 
 loaf was smaller than the others. These experiments indicated that 
 flours of high food value but poor bread-making properties may be 
 blended so as to produce a better balanced gluten than that contained 
 in either the hard-wheat or soft-wheat flours. The bread produced, 
 however, is not equal in quality to that from wheat normally containing 
 a well-balanced gluten. 
 
 In the course of these experiments tests were made of the effect of 
 the temperature of the flour when mixed upon its bread-making 
 properties. In these tests better results were obtained with flour at 
 70^ C. (158° F.) than with flour at a temperature considerably higher 
 or lower. There is, therefore, a reason for the common household 
 practice of warming flour in cold weather before mixing the dough. 
 Care should be taken, however, not to heat the flour too much. In 
 
352 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 
 
 the experiments referred to, keeping the flour for some time at the 
 highest temperature (100"= C. or 212° F.) had a decidedlj' deleterious 
 eflect upon its bread-making properties. 
 
 LOSSES OF MATERIAL IN BREAD MAKING. 
 
 All processes of bread making entail some loss aside from that of 
 flour and dough accidentally lost in the mixing, but the greatest loss 
 occurs during the production of leavened bread by fermentation. The 
 action of the j'east and the heat at different stages of the process 
 results in the fermentation of carbohydrates and the production of 
 carbon dioxid and alcohol, and other simple bodies from the complex 
 starches, nitrogenous bodies, etc., originally present. 
 
 Inasmuch as many of the compounds formed during the fermentation 
 process are either gaseous or volatile at the temperature of baking, 
 there is opportunity for appreciable loss of material. This has such 
 an important bearing upon the nutritive value of flour that considerable 
 study has been made of the kinds and quantities of material lost in 
 bread making. As a result of experiments carried on at the Minnesota 
 and Mew Jersey stations, it has been estimated that when care is 
 exercised in making bread the amount of nutritive material lost need 
 not exceed 1.5 per cent of that in the flour; but in careless bread 
 making the loss was equal to 8 per cent of the nutritive material of 
 the flour, and it could even be more. The loss in the former case 
 would be equivalent to about 3 pounds of flour per barrel, and in the 
 latter case 15 pounds or more. 
 
 This loss affects both protein and carbohydrates to an appreciable 
 extent. Some very careful experiments in bread making, carried on 
 as part of these nutrition investigations in a bakery in Pittsburg, 
 showed an average loss of 1.3 per cent of the total protein and 3.2 per 
 cent of the carbohydrates of the flour in the process. There was also 
 a slight loss of fat, due apparently to its volatilization by the heat of 
 the oven. 
 
 Some destruction of protein compounds in bread making is unavoid- 
 al)le when yeast is used, as nitrogenous material is required by the 
 yeast for growth. in the process of fermentation, but fortunately it is 
 nonproteid rather than proteid material that is thus utilized, and the 
 amid compounds of the flour, which have practically no nutritive 
 value, may serve to .some extent for this purpose. 
 
 The loss of carbohydrate material is due chiefly to the formation of 
 alcohol and carbon dioxid by the yeast in growing, both being largely 
 expelled from the bread when it is baked. In addition to these there 
 is also a small amount of carbon lost in other forms, such as volatile 
 acids produced during the fermentation process. As in the case of the 
 nitrogen, some loss of this kind is unavoidable, since the production of 
 
WHEAT FLOUE AND BREAD. 353 
 
 gas to leaven the dough' is the object of the fermentation. In these 
 experiments, in which special care was taken in the bread making, the 
 volatile products from carbon given off were equivalent to a loss of 
 1.68 per cent of the total starch present. It is apparent, then, that the 
 proper course of procedure is to stop the fermentation when sufEcient 
 gas has been produced to render the dough as porous as is desired, 
 because f ui-ther continuation of the process results simply in a destruc- 
 tion of carbohydrates to no purpose. 
 
 The important feature of the art of producing leavened bread thus 
 lies in proper fermentation. Unless this process has been allowed to 
 proceed far enough, a heavy, soggy, unappetizing loaf is the result; 
 while if it is allowed to proceed too far there is a considerable loss of 
 material, and an objectionable quality is imparted to the bread by 
 the development of acid. 
 
 Several attempts have been made to introduce methods of leavening 
 that would not cause a destruction of nutritive material. One of 
 these is the Dauglish method, by which the so-called aerated bread is 
 produced. This method consists in mixing the flour with water charged 
 with carbon dioxid under pressure. The bread is about as porous as 
 that raised with yeast, but is less agreeable to the taste of many per- 
 sons, apparently because of a lack of the bj^-products resulting from 
 the action of the yeast in the fermentation process. Baking powders, 
 that is^ mixture^s which liberate carbon dioxid when moistened, are 
 used to a considerable extent in making cake and quick-rising breads, 
 biscuits, etc., but the attempts to substitute them entirelj^ for yeast 
 have not met with much success. Some of the objections to them are 
 that they may be easily adulterated, and that bread made by the use of 
 them lacks the flavor and aroma of well-made yeast bread. 
 
 THE COMPOSITION OF BREAD. 
 
 The composition of bread depends primarily upon that of the flour 
 froiirwhich it is made. If milk and butter (or lard) are used in mix- 
 ing the dough, as is commonly the case, their nutrients are, of course, 
 added to those of the flour ; but when only water and flour are used 
 the nutrients of the bread are simply those of the flour. In either 
 case, however, the proportions of the nutrients in the bread are smaller 
 than those in the flour, because a considerable part of the moisture 
 from the water or the milk used in mixing the dough is present in the 
 bread after baking, that is, a pound of the bread would contain less of 
 any of the nutrients than a pound of the flour, because the proportion 
 of water in the bread is greater. The following table shows how the 
 composition of flour compares with that of bread, the different kinds 
 
354 YEAEBOOK OF THE DEPARTMENT OF AGRICULTITKE. 
 
 of bread all having been made from the flour with which they are here 
 compared : 
 
 Composition of four and ofliread made from it in different ways. 
 
 Material. 
 
 Water. 
 
 Protein. 
 
 Fat. 
 
 Carbohy- 
 drates. 
 
 Ash. 
 
 
 Per cent. 
 10. J 1 
 36.12 
 37.70 
 36.02 
 
 Per cent. Per cent. 
 12.47 0.86 
 
 Per cent. 
 76.09 
 53.70 
 51.70 
 52.63 
 
 Per cent. 
 0.47 
 
 Bread from flour and water 
 
 9.46 
 
 .40 
 
 .32 
 
 
 9.27 
 10.57 
 
 1.02 
 
 .48 
 
 .31 
 
 Bread frota flour and skim millc 
 
 .30 
 
 It is thus shown that the proportion of water is larger and that of 
 each nutrient smaller in bread than in flour, and that the nutrients of 
 the flour are increased by those of nutritive materials added in making 
 the bread. 
 
 It is apparent that two kinds of bread from the same lot of flour 
 may differ, according to the method used in making the bread. On 
 the other hand, two loaves of. bread made by exactly the same process, 
 but from different lots of flour of the same grade or brand, would not 
 necessarily have the same composition because of a possible variation 
 in the flours. The chemical composition of wheat is not a fixed char- 
 acteristic, different kinds of wheat varying widely in this respect. 
 Furthermore, the composition of the same sort of wheat varies with 
 several factors, such as climate, rainfall, and the soil on which it is 
 grown. It is evident, therefore, that statements regarding the compo- 
 sition of flour can hardly be definite. 
 
 GRAHAM, ENTIRE WHEAT, AND STANDARD PATENT FLOURS. 
 
 Inasmuch as the composition of bread is so dependent upon, that of 
 the flour, a consideration of the different grades of flour on the market 
 will afford an understanding of how the breads from them compare in 
 this respect. Attention is here given more particularly to Graham, 
 entire wheat, and standard patent flours, as these are the three grades 
 most commonly used, and hence of most importance. Graham flour, 
 strictly ^speaking, is simply wheat meal, that Js, the entire grain 
 ground to a powder. It has sometimes been made by removing the 
 outer branny portions of the kernel and grinding this separately from 
 the inner parts, afterwards combining the two, as it was thought that 
 the efforts to grind the naturally coarse material with the resjt of the 
 wheat had a deleterious effect upon the bread-making qualities of the 
 flour. It is now commonly made by crushing and grinding the_whole 
 of the kernel at once, without bolting or sifting. When thus prepared 
 it contains the same ingredients as the wheat itself and in the same 
 
 proportions. Such flour is coarse, however, and 
 
 even the most 
 
WHEAT FLOUK AND BREAD. 355 
 
 successful attempts at fine grinding^ still leave it fairly coarse and with a 
 lai^ejxapQrtian of branny particles.) To overcome this objection 
 more or less bolting is frequently resorted to. Much of the flour sold 
 as Graham has been thus treated, though, of course, such a product is 
 not really Graham flour. 
 
 The term_J^ntire j«tbeai^wou-l4-strggest flour practically identical 
 with the Graham. The flour thus designated, however, it is often said 
 is made by first decorticating the grain, or removing the branny outer 
 covering, and grinding the remainder. By such a method some of the 
 outer portion of the wheat kernel would be retained in the flour, only a 
 small proportion of the wheat being discarded. So far as can be learned 
 some of the so-called whole-wheat flour is not so ground, but is made 
 by including with the patent grades the middling and low-grade flours 
 with considerable of the germ. Whole-wheat flour is not so coarse as 
 Gr aham nor so fine, as the white ilours! ' —- 
 
 The finer grades of patent flqur contain neither the bran nor the germ 
 of thewheat. In some of the Tower grades^ tbe^^rm is retained, and 
 as this part is somewhat ricjfier than the rest of the kernel in protein, 
 the proportion of this ingredient is larger in the lower than in the 
 higher grades of flour. The chief reason for removing the germ in 
 milling the higher grades' is that, because of the presence of the oil, 
 which is more abundant in the germ than in the remainder of the wheat, 
 flour in which it is retained has a tendency to become rancid and to 
 deteriorate in bread-making properties. The bran is left out because 
 of its coarse nature and because it dai-kens the flour. The grade of 
 white flour most widely used is that known as straight patent, or 
 standard patent, or family grade. Although this flour contains neither 
 the germ nor the bran of the wheat, in modern exhaustive milling 
 nearlj" 73 per cent of the kernel is recovered in this grade. 
 
 Because the proportion of nitrogenous material in both the germ and 
 the outer portions of the wheat is larger than in the remainder of the 
 kernel, it has been popularly contended that the flours from which 
 these portions have been removed are less nutritious than those in which 
 they are retained in the milling. In support of this conteiifeon the 
 diiierent grades of flour have frequently been companed with respect 
 to the proportions of protein in them, apparently to t^ie advantage of 
 the coarser grades. In consideration of what has alread}^ been shown 
 regarding the variable composition of wheat, however, it is evident 
 that differences in the proportions of nutrients in the different grades 
 of flour as purchased in the market would much more likely be due to 
 differences in the wheat from which they were ground than to advan- 
 tage in any particular method of milling. Patent flour from<5vheat 
 with 15 per cent of protein would contain larger proportions of the 
 nutrient than Graham flour from wheat with only 8 per cent, such 
 differences in protein content being not at all uncommon. Obviously, 
 
356 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 
 
 therefore, the only fair comparison is that between the three grades 
 of flour milled from the same lot of wheat. These points are clearly 
 illustrated by the figures in the following table, perfectly uniform 
 results having been obtained at both the Maine and Minnesota experi- 
 ment stations: 
 
 Voinposilio)! of fours and breach, «s shown by recent experiments. 
 
 Material. 
 
 Minnesota wheat flour (fresh material): 
 
 First patent 
 
 Second patent 
 
 Standard patent ' 
 
 First clear 
 
 Second clear 
 
 ' ' Hed dog " 
 
 Entire wheat 
 
 Graham 
 
 Oregon wheat flour (fresh material); 
 
 Standard patent 
 
 Entire wheat ^ 
 
 Graham 
 
 Oklahoma wheat flour (fresh material): 
 
 Standard patent...' 
 
 Entire wheat 
 
 Graham 
 
 Bread made from Oregon wheat flour (water-free 
 basis) : 
 
 Standard patent 
 
 Entire wheat 
 
 Graham 
 
 Bread made from Oklahoma wheat flour (water- 
 free basis): 
 
 Standard patent 
 
 Entire wheat 
 
 Graham 
 
 Bread made from ]>atent flour (fresh material): 
 
 High grade 
 
 Standard grade 
 
 Medium grade 
 
 Low grade 
 
 Water. Protein. : Fat. hydrates. ^^'^■ 
 
 Per cent. 
 10.55 
 10.49 
 10.54 
 10.13 
 10. US 
 
 9.17 
 10.81 
 
 8.61 
 
 8.94 
 8.66 
 
 S.15 
 
 9.93 
 
 7.4i; 
 
 7.73 
 
 Per cent Per cent. 
 
 32.9 
 34.1 
 39,1 
 
 40.7 
 
 11.08 j 
 11.14 
 11.99 [ 
 13.74 ! 
 15.03 ' 
 18.98 
 12.26 
 12.65 
 
 7.55 
 ,8.26 
 8,97 
 
 15.06 
 16.63 
 16.81 
 
 8,32 
 9,49 
 9,94 
 
 16,24 
 18,06 
 18.43 
 
 9.0 
 10.6 
 12.6 
 
 1,15 
 1.20 
 1.61 
 2.20 
 3.77 
 7.00 
 2.24 
 2.44 
 
 1.25 
 1.67 
 1.68 
 
 .92 
 1.64 
 1.79 
 
 1.37 
 1.82 
 1.83 
 
 1.02 
 1.77 
 1.94 
 
 1.4 
 l.S 
 1.2 
 1.1 
 
 Per cent. 
 76.85 
 76. 75 
 75.36 
 73.13 
 69.37 
 61.37 
 73.67 
 74.58 
 
 •SI. 82 
 80.35 
 79.48 
 
 73.05 
 72. 33 
 
 87. 24 
 85. 72 
 
 82.03 
 
 7S. 75 
 77. 12 
 
 56.6 
 54.9 
 48,3 
 44.3 
 
 Per cent. 
 
 0.37 
 
 .42 
 
 .50 
 
 ,80 
 
 1,75 
 
 3,48 
 
 1,02 
 
 1.72 
 
 ,44 
 1,07 
 1,72 
 
 ,52 
 1,22 
 1,32 
 
 1,38 
 1,45 
 2,51 
 
 ,71 
 1,60 
 2,51 
 
 For the experiments with Minnesota wheat the flours were ground 
 by one of the large mills in Minneapolis. In addition to the three 
 flours under discussion, all the grades of flour commonly ground were 
 produced from this wheat, and obtained for analysis, the results being 
 given in the table. The first patent is the highest grade of flour manu- 
 factured; the gluten in it has a greater power of expansion than that 
 in any other grade, and the loaf made is the largest and whitest. Sec- 
 ond patent is somewhat similar to first patent, but the gluten has not 
 quite so high a power of expansion, and the bread is a shade darker. 
 The first clear grade, which comprised about 12 per cent of the wheat, 
 is obtained after the first and second patent have been removed. This 
 
WHEAT FLOUR AND BREAD. 357 
 
 grade contains slightlj' more protein than either of the two patent 
 grades, but the gliadin and glutenin are not present in such favorable 
 proportions for bread making. All three of these flours are combined 
 to produce the straight or standard patent flour. The quantity of first 
 or second patent flour put upon the market is relatively small com- 
 pared with that of standard patent. 
 
 After the standard patent flour has been removed there is still 
 obtained about 0.5 per cent of a flour called second clear, or low grade, 
 which contains a high percentage of protein, but with a gluten of poor 
 quality for bread making. Finally there is the so-called "red dog" 
 iiour, the lowest grade produced, which is secured mainly from the 
 germ or embryo and adjacent parts of the wheat. It contains large 
 proportions of protein and fat, but the proteids of the wheat germ are 
 decidedly dift'erent from gluten in character and composition. Germ 
 flour has poor agglutinating properties, and little power of expansion, 
 and produces a poorly raised, dark-colored loaf. 
 
 The entire wheat flour included in this list was produced by removing 
 a portion of the bran coat and grinding the remainder of the kernel. 
 The Graham flour was made by grinding the whole of the grain, bran 
 and all, no sieves or bolting cloths being used. 
 
 The Oregon wheat and the Oklahoma wheat were both ground at 
 the Minnesota station in a small mill procured especially for the inves- 
 tigations. Only the standard patent, entire wheat, and Graham flours 
 were produced from either of these wheats. It will be noticed that 
 the Oregon wheat was much poorer in protein but richer in carbo- 
 hydrates than the Oklahoma wheat, while the Minnesota wheat was 
 about midway between. The analj'ses of these samples will .serve to 
 illustrate what has been stated above regarding the comparison of 
 different grades of flour from different lots of wheat. Graham ffour 
 from even the Minnesota or the Oklahoma wheat had a larger protein 
 content than the standard patent from the same wheat; but, on the 
 other hand, the standard patent from either had much more protein 
 than the Graham from the Oregon wheat. It is quite apparent, there- 
 fore, that a comparison of composition of the different grades from 
 different lots of wheat is not a fair one. \ 
 
 Comparing the three grades of flour from the same lot of wheat, it 
 will be noticed that in each case the proportion of protein was largest 
 in the Graham and smallest in the standard patent flour, the entire 
 wheat being between these two. On the other hand, the proportion 
 of carbohydrates was smallest in the Graham and largest in the standard 
 patent flour. Considering that these two nutrients are not present in 
 flour in proper proportions for a well-balanced diet, there being an 
 excess of carbohydrates and a deficiency of protein, it might seem 
 from such a comparison of composition that the coarser flours would 
 be the best. Before an adequate discussion of relative nutritive value 
 
358 YEARBOOK OK THE DEPARTMENT OF AGRICULTURE. 
 
 is possible, however, the digestibility of the three flours must be 
 determined. 
 
 The breads from the different flours, when made in such ways as to 
 afford comparison, bear the same relation to one another as the flours 
 in respect to the proportions of nutrients. This is what would be 
 expected in view of the fact, already stated, that except for the 
 materials added in mixing the dough the composition of the bread 
 depends' entirely upon that of the flour. The analyses of breads 
 included in the table will illustrate this. Thus, in the breads made 
 from different grades of patent flour, that from the high-grade flour, 
 which had the lowest protein content, had the least pi'otein, while that 
 from low-grade flour, wl^ich is the richest in protein, had the most. 
 This was the case with the breads of which the analyses are given in 
 the table, even though the proportion of water is highest in the bread 
 from the low-grade flour; if the computations were based upon the 
 dry matter of the breads the differences would be still larger. In the 
 case of breads made from the different grades of Oregon and Oklahoma 
 wheat, the values given are for dry matter, in order that the com- 
 parison may be absolute. These data show that in each case the 
 Graham bread had the most protein and the least carbohydrates, as it 
 was with the flours. 
 
 THE DIGESTIBILITY OF BREAD. 
 
 A knowledge of the digestibility of any food material is of prime 
 importance for two reasons: In the first place, unless it is completely 
 digested a portion of it does not serve to nourish the body at all, 
 because only that part of the food that is digested and absorbed from 
 the alimentar}' canal can.be thus utilized, and, in the second place, 
 some indigestible materials act as irritants in the alimentary canal, and 
 while they may stimulate the excretion of the digestive juices they 
 sometimes increase peristalsis, thus hastening the contents along too 
 rapidly to permit complete absorption, with the result that nutritive 
 material which otherwise might be absorbed and serve to nourish the 
 body is lost with the indigestible materials. In estimating the nutri- 
 tive value of a food material, it is therefore necessary to consider not 
 only its composition, but also, and more particularly, the proportions 
 of its different nutrients that are digested and utilized. 
 
 In connection with the nutrition investigations at the Maine and 
 Minnesota stations, upward of 100 digestion experiments have been 
 made with young, healthy men, with bread from different grades of 
 flour ground from hard and soft wheats from Indiana, Michigan, 
 Minnesota, Dakota, Oklahoma, and Oregon. In these investigations 
 great care was given in each case to the securing of different grades of 
 flour from the same lot of wheat, to the production of bread from the 
 flours, and to all other details of the experiments, in order to secure 
 
WHEAT FLOUR AND BREAD. 859 
 
 uniformity of conditions, and thus insure fairnes.s and leliahility in 
 comparison. The results of these experiments therefore give very 
 definite information regarding the relative digestibility of bread from 
 different grades of flour. 
 
 The larger number of these experiments wore made with Graham, 
 entire wheat, and standard patent flours from wheats from difterent 
 sections of the country. The averages of the results with these three 
 grades of flour gi\-e the following as the proportions of nutrients that 
 were digested from the different flours, these factors being commonly 
 termed coefficients of digestibility: Standard patent flour, protein 88.6 
 per cent and carbohydrates 9T.7 per cent; entire wheat flour, protein 
 82 per cent and carbohydrates 93.5 per cent; Graham flour, protein 
 74.9 per cent and carbohydrates 89.2 per cent. 
 
 The digestibility of the fat was also determined in some cases, but 
 for the most part the results were believed to be too low, and are 
 therefore omitted. The quantity of fat in bread is too small to permit 
 of accurate tests of its digestibility. This is a matter of no importance, 
 however, as bread is not considered as a source of fat in the diet. The 
 very common custom of eating butter or some other fat with bread is 
 in reality But a method of supplj'ing this deficiency. 
 
 It will be seen that there is a considerable difference in the digesti- 
 bility of the nutrients in the three kinds of bread, the variations in the 
 protein being larger than those in the carbohydrates. For both nutri- 
 ents the digestibilitj' of the standard patent flour was the greatest, and 
 that of the Graham flour was least. This is true not only for the aver- 
 ages of the tests with the different flours, but also for the individual 
 tests. With some of the wheats the differences in the proportions 
 digested from the different flours were not so wide as with others; and 
 in some cases also there were very noticeable differences between the 
 subjects with respect to the completeness of digestion; but with all the 
 subjects, and with all kinds of wheat thus far tested, the unifoi-m result 
 was that the digestibilit}' of the standard patent flour was. the highest, 
 that of entire wheat the next, and that of Graham the lowest. Con- 
 cordant results were obtained in artificial digestion experiments. 
 
 Experiments were made with first, second, and standard patent 
 flours to learn how these compare with one another, the digestibility 
 of the nutrients as determined in these tests being as follows: First 
 patent, protein 90.5 per cent and carbohydrates 98 per cent; second 
 patent, protein 91.4 percent and carbohydrates 98.7 per cent; stand- 
 ard patent, protein 90.3 per cent and carbohydrates 97.4 per cent. 
 
 Practically, there was no difference in these three grades of patent 
 flour with respect to the proportions digested; and since the proportion 
 of protein is much the same in all of them, they are about equal in 
 actual nutritive value. 
 
 Diflferences in digestibility of the flours containing the branny por- 
 tion of the wheat are sometimes atti-ibuted to the fineness with which 
 27658—04 2 
 
360 TEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 
 
 the coarse materials are ground. This is doubtless true to some 
 extent, and may in part explain why whole wheat is more digestible 
 than Graham, because the whole-wheat flour is somewhat more finely 
 ground. But even when bran is reduced to a very fine powder it is 
 not so well digested as flour, and its presence in the flour decreases 
 rather than increases its nutritive value, because it decreases the 
 digestibility. This was observed at the Minnesota station in some 
 experiments with Oklahoma wheat. Bran removed in producing the 
 patent flour was ground very fine, and was added to some of the flour, 
 14 per cent as much bran as flour, or about the proportion in which it 
 was removed during the milling. This increased the protein content 
 of the flour to 15.3 per cent as compared with 15.1 per cent in the 
 flour without the bran. The digestibility of bread made from this 
 mixture, as compared with that of bread from the same flour without 
 the bran, was as follows: Bread with bran, protein 85.9 per cent and 
 carbohydrates 93.3 per cent; bread without bran, protein 91.6 per 
 cent and cai'bohydrates 97.8 per cent, 
 
 Thus, while the addition of the bran to the flour increased the pro- 
 portion of the nutrients but a trifling amount, it decreased the digesti- 
 bility very decidedly, so that the digestible nutrients in the flour with 
 bran were only 13.2 per cent of protein and 67.5 per cent of carbo- 
 hj'drates, while in the same flour without the bran they were 13.8 per 
 cent of protein and 71.1 per cent of carbohydrates. What little was 
 gained in increase of nutrients by the addition of the bran was more 
 than offset by the failure of the bran to be digested. It is evident, 
 therefore, that the defective digestibility of the bran is not due 
 entirely to imperfect grinding, though it is worthy of note that the 
 bread from the mixture of ordinary flour and finely ground bran was 
 more digestible than that from either Graham or entire wheat flour 
 from the same lot of wheat. 
 
 A number of experiments were also made to study the effect of 
 adding germ to patent flour. As in the experiments with bran, the 
 germ removed in milling standard patent flour from Oklahoma wheat 
 was finely ground and mixed with some of the standard patent flour 
 in the proportion in which it was removed during the milling, the 
 mixture containing about 93 per cent flour and 7 per cent germ. The 
 digestibilitj' of the nutrients of bread made from this mixture was as 
 follows, the data for the patent flour without the germ being also 
 given for comparison : 'Bread from mixture, protein 90 per cent and 
 carbohydrates 97.6 per cent; bread from patent flour, protein 91.6 
 per cent and carbohydrates 97.8 per cent. 
 
 The digestibility of the protein in the flour with the germ added 
 was slightly less than in the same flour without the germ, while that 
 of the carbohydrates was practically the same in both. The digestible 
 nutrients in the flour with the germ, computed by use of these results, 
 
WHKAT FLOL'K AND BREAD. 861 
 
 would give a trifle more protein and slightly less carbohydrates than 
 in the flour without the germ. There was, therefore, practically no 
 gain in nutritive value by retaining in the flour the germ that is 
 ordinarily removed in the milling. 
 
 THE NUTRITrVE VALUE OF BREAD. 
 
 AS| previously pointed out, bread contains from 35 to iO per cent of 
 water. Since the remainder, about 60 per cent at least, is nutritive 
 material, bread is really one of the most nutritious of the common 
 foods, but few others equaling it in this respect. Bread supplies a 
 large amount of carbohydrates, a moderate amount of protein, a small 
 amount of mineral matters, and almost no fat. Since there is relatively' 
 an excess of carbohydrates and a deficiency of protein in wheat, bread 
 could not serve alone for proper nutrition of the body, because an 
 amount of bread sufficient to supply the requisite protein would fur- 
 nish much more carbohydrates than necessary. In a mixed diet this 
 discrepancy is of little importance, because the deficiency of protein is 
 made up by such foods as meat or cheese. Bread and milk forms a 
 much more suitable diet than bread alone. Where bread forms the 
 whole or the main part of the diet, as it does among the larger num- 
 ber of poor people, and when flours of low protein content are used, 
 the deficiency of protein is of much more consequence. In case of 
 flours of high protein content this deficiency is of course smaller. 
 
 Various methods of increasing the protein content of bread have 
 been followed, but only a few of them have been adopted for ordinary 
 practice, because of a tendency to increase the cost of the bread too 
 much. The use of skim milk instead of water for mixing the dough 
 does not increase the cost of the bread very materially, but it does add 
 appreciably to the protein content. A comparison of skim-milk bread 
 with water bread, made from the same flour, is given in the table on 
 page 354, showing that the skim milk increased the protein to the 
 extent of about 2 per cent. 
 
 CONCLUSION. 
 
 In this discussion especial consideration has been given to the protein 
 and carbohydrates, and no mention has been made of the mineral 
 matters, among which are the phosphates of the wheat so popularly 
 considered of especial virtue. This omission has been intentional for 
 the reason that as yet not enough is known concerning the metabolism 
 of mineral matters in the body to warrant a discussion of the value of 
 those contained in the flour. Such investigations as have been made 
 suggest that the supply in the ordinary diet is more than sufficient to 
 meet the demands of the body. In the experiments it was observed 
 that the quantity of mineral matters in the feces was from a third to a 
 half as large as those in the bread, but it can not be said how much of 
 
362 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 
 
 the excreted material pertained to undigested bread and how mucli 
 was from other sources. In view of such lack of knowledge it woul|l 
 be futile as yet to compare the three grades of flour with respect fO 
 their value as sources of mineral matter. 
 
 While the coarser grades are not more nutritious than the tiner 
 flours-, there are man}' cases in which they are especiall}'' desirable, as, 
 for instance, for persons of sedentary habit and occupation, becaus^ 
 their stimulating of the alimentary tract may help to procure a larger 
 secretion of the digestive juices and also to overcome a tendency to 
 constipation. This, however, is a purel}' phj'siological action, and 
 should be considered apart from the nutritive value. Finally, it may 
 be said that wheat flour of all the various grades is one of the cheapest, 
 most digestible, and most nutritious of human foods, and well worthy 
 of the high estimation in which it is generally held. The use of dif- 
 ferent sorts of wheat flour is a convenient waj' of giving variety to the 
 diet, a matter which is of no little importance.