F :->39 E7 913 opy 1 AIRY mMmmt c]es. Q. How soon after parturition does the milk become normal? A. Usually in four or five days. In occasional cases it ma_\' remain abnormal for fifteen days. DIVISION TWO. CREAM. Q. What is cream? A. Cream consists of all the portions of milk after a part of the milk serum has been removed. Ordinarily cream is that portion of milk which rises to the top in a layer, upon letting milk stand for a time, or is separated from it by centrifugal force. Standard cream contains at least IS per cent, of butter fat. Q. Why does cream rise on milk? A. Cream contains more butter fat than milk and since butter fat is the lightest constituent of milk, it rises for the same reason that wood floats on water. Q. How is cream separated from milk? A. By difterent systems : (1) The Shallow Pan System. — Milk is set in shallow pans for 24 to 36 hours, during which time the cream rises to the to]). The shallow pan system will usually leave from .4 per cent, to l.o per cent, of fat in the skim milk. (2) The Dilution System. — Milk is diluted with water, either warm or cold. The cream rises quickly, but the skimming is in- efficient and the feeding values of the skim milk is lessened. This system usuallv leaves from .7 to 1.5 per cent, of fat in the skim milk. (■V) The Deep Setting System. — Milk is set in deep narmw cans, 8 to 10 inches in width and IS to 24 inches in depth. The cans are set in cold or ice water. The difference in temperature between the warm milk and the cold water in which it sets causes cream to rise rapidly in the milk, due to the fact that the extreme difference in temperature causes a vertical circulation at such a rapidity that the lighter parts of the milk are carried to tlie top with the current, and are prevented from being carried dcvwn on account of their lightness. This system usually leaves from ..3 ti .5 per cent, of fat in the skim milk. BUTTER 11 (4) The Centrifugal System. — Cream is separated by centri- fugal force. The milk flows into a bowl, rotating very rapidhs causing the heavier constituents such as milk sugar, casein, albu- men and ash, ito fly to the outside, while the lighter butter fat flows toward the center of the bowl, carrying with it some of the other constituents. The centrifugal system should leave less than .1 per cent, of fat and when operated with care from .02 to .05 per cent, of fat. Q, What is the composition of cream? A. Cream (containing IS per cent, to 30 per cent, of butter fat) has about the same per cent, of sugar, albuminoids and ash as milk. The fat varies decidedly and replaces the water in the cream. The per cent, of fat in cream may range from 18 per cent, to 80 per cent., according to the manner of skimming. An average cream contains about 22 per cent, of butter fat, 69 per cent, of water, 3.8 per cent, of albuminoids, -t.G per cent, of sugar, .6 per cent, of ash. Retail cream averages lower in butter fat. It is de- sirable that cream for butter-making contain about 3.") per cent, of butter fat. Q. What gives the heavy consistency to some market cream which is low in butter fat? A. It may contain condensed milk, it may contain viscogen or it may be homogenized. Q. What is viscogen? A. It is a 50 per cent, sugar solution mixed with lime water forming sucrate of lime. Q. What is homogenized cream? A. It may be cream which has been put through a homo- genizer, a machine which forces the cream through a small open- ing under \ery high pressure against a hard surface. This divides the fat globules so finely that the friction on the surface of the globules is greater than the difl^erence betwieen the specific gravity of fat and milk serum and consequently they will not rise by grav- ity. The cream is rendered very \-iscous and appears riclier than before homogenizing. Homogenized cream is sometimes made from an emulsion of skim milk and butter fat from butter, run through a homogenizer. Some ice cream makers make use of the latter since it is a cream product which may be had from stored goods at anv time. DIVISION THREE. BUTTER. Q. What is butter? A. Butter is the product of gathering in any manner the fat of fresh or ripened cream or milk into a mass with a small propor- tion of the other milk constituents. It may or may not contain salt. 12 BUTTER Q. What is the average composition of butter? A. Water lo per cent. Butter fat 83 per cent. Curd 1 per cent. Ash and Salt o per cent. 100 per cent. Q. What is the variation in the per cent, of water in butter? A. From 6 per cent, to 16 per cent. More than 16 per cent, of water can be incorporated but, according to the Federal stand- ard, butter containing 16 or more per cent, of water is considered adulterated. Q. What is the range in per cent, of butter fat in butter? A. From 82y2 per cent, to 94 per cent. Butter may contain less than 82^ per cent, of fat but it is not standard butter accord- ing to the Federal standard. The Ohio standard calls for at least .80 per cent, of butter fat in butter. Q, What is the range in per cent, of curd in butter? A. From .5 per cent, to 4 per cent. Q. What is the range in per cent, of salt in butter? A. From none to S per cent. When there is more than 4 per ■cent., part of it is undissolved and the butter is gritty. Q, What is the overrun in butter^niaking ? A. The difference between the weight of churned butter and the butter fat in the milk or cream. Q. What causes overrun? A. The incorporation of water, salt, curd and ash in the pro- cess of churning. Q. What is the per cent, of overrun? A. The per cent, that the overrun is of the butter fat in the milk or cream. Q. How are the overrun and the per cent, of overrun calcu- lated? A. Suppose a butter maker secures 162 pounds of butter from 450 pounds of cream testing 30 per cent, of butter fat? .30 X 450 = 135.00 pounds butter fat in the cream. 162 — 135 =: 27.00 pounds overrun. 27 X 100 = 2700. 2700 ^ 135 = 20% overrun. Q. What is the usual per cent, of overrun? A. From 8 per cent, to 21.21 per cent., depending on the amount of water and curd incorporated. An overrun of 21.21 per cent, can be obtained in making standard butter containing 82^4 per cent, fat only when there is no loss of fat in churning. This is not possible in practice. OTHER MILK PRODUCTS 13 Q, Can the amount of butter be calculated if the weight of the butter fat is known? A. Approximately, if one knows the per cent, of overrun usually obtained. Ordinarily in calculating the amount of butter that may be made from milk the overrun is counted IT per cent, or about 1/6; therefore adding 17 per cent, or 1/6 to the butter fat would give the amount of butter. In starting with cream it is usually taken as 20 per cent, or 1/5. Q. How much butter may be made from 900 pounds of cream containing 30 per cent, of butter fat? A. .30 X 900 = 270.00 pounds of butter fat. Suppose the usual overrun secured by the butter-maker is 18 per cent. Then .18 X 370 = 48.6 pounds overrun. 370 + 48.6 = 318.6 pounds butter, or 1.18 X 270 = 318.6 pounds butter. If we assume 20 per cent, to be the per cent, of overrun, then .20 X 270 = 54.00 pounds overrun. 270 + 54 = 324.00 pounds butter, or 1.20 X 370 = 324.00 pounds butter, or 1/5 of 270 = 54.00 pounds overrun. 270 + 54 = 324.00 pounds butter, or 1 1/5 X 370 = 324.00 pounds butter. Q. If a cow gives 8,000 pounds of milk testing 5 per cent. butter fat in one year, how much butter fat will she produce and to how much standard butter containing 82^ per cent, of butter fat is it equivalent? A. .05 X 8000 = 400.00 pounds butter fat in year. 400 X 100 = 40,000. 40000 -^ 82.5 = 484.84 pounds of standard butter con- taining 82^^ per cent, of butter fat. DIVISION FOUR. OTHER MILK PRODUCTS. Q. What is skim-milk? A. Skim-miik is that portion of milk remaining after cream is extracted; or, in other words, it is the milk serum, though it may contain a small per cent, of fat. The amount of fat remaining depends upon how thoroughly the milk has been separated. Q. Of what is skim-milk composed? A. Skim-milk has about the same per cent, of solids not fat as whole milk, except about 2 per cent, to 2^ per cent, more water, and a small amount of butter fat (about .1 to .3 of one per cent.) which cannot be separated practically from the milk. Q,.What is skimnmilk used for? 14 OTHER MILK PRODUCTS A. In foreign countries it is largely used for human food, but in the United States it is mostly fed to young farm animals. Some of the things made from skim-milk are certain kinds of cheese, fer- mented milks, cold water paints, skim milk powder, patent foods and a material for sizing paper. Condensed skim-milk is used largely in ice cream making. Q. What function does it perform in the body? A. Skim-milk contains all the constituents which furnish food for muscle and bone, and in the same form and per cent, as that of whole milk. It also contains one of the constituents that produce heat, namely, milk sugar. Q. What is buttermilk? A. Buttermilk is the residue of the cream after the butter is churned. In other words, it is cream with the butter fat taken out of it. Q. What is the coimposition of buttermilk? A. Buttermilk is similar to skim-milk except in milk sugar. Its composition, however, like that of skim-milk, varies. Average butter milk contains about 0.3 per cent, solids, of which 4.6 per cent, is lactic acid and milk sugar, 3.T per cent, casein and albumen, .3 per cent, butter fat, and .7 cent. ash. Buttermilk, like skim- milk, is used for human food, for feeding young animals, and, to a small extent, is used in manufacturing buttermilk cheese. It is also used for medicinal purposes, and is considered one of the most wholesome drinks. Q. How is artificial buttermilk prepared? A. By heating skim-milk to 165 deg. F. for at least 10 min- utes, cooling to 70 deg. F., and adding 5 to 10 per cent, of good starter or culture of lactic acid bacteria. As soon as the milk has coagulated it is cooled to about 50 deg. to 55 deg. F. It is then placed in a churn and churned for five minutes or until well emul- sified. Q. How are fermented milks prepared? A. Skim-milk is pasteurized, then cooled, and a culture of acid producing bacteria added. Bacillus Bulgaricus is much used for this purpose in connection with other varieties. Bacillus Bul- garicus grows best at a temperature of 85 deg. F. to 100 deg. F. It is capable of producing much more acid than ordinary lactic acid bacteria. Q. What is the percentage composition of cheese? A. Roughly speaking a well cured cheese consists of 1/3 water, 1/3 butter fat and 1/3 curd. A green Cheddar cheese contains about 37 per cent, water. 34 l>er cent, fat, 24 per cent, casein and 5 per cent, milk sugar, lactic acid and ash (chiefiv salt). OTHER MILK PRODUCTS 15 Q. How much cheese can be made from 100 pounds of milk? A. From 8 to 14 pounds, the average being about 10 pounds. Q. Does the composition of the milk influence cheese yield? A. Yes. The richer the milk in fat and casein the greater the cheese yield. Q. How may approximate cheese yield be calculated? A. (l)\\'hen the per cent, of fat and casein in milk are known, (per cent, of fat -(- per cent, of casein) X 1-63 =: yield per 100 pounds of milk.* (2) When only the per cent, of fat is known (2.3 X per cent, of fat) — 1.4 ^ yield per 100 pounds of milk.* Q. What is the by-product of cheese? A. Whey. Q. What is the composition of whey? A. Whey is composed of about G.T per cent, of solids, of which 5." per cent, is milk sugar, .) pipette, (4) acid measures and (5) dividers. TESTING MILK 19 Q. Are there any chemicals used in making the test? A. Ves ; one — commercial sulphuric acicl. Q. What are the different steps in testing milk with the Bab- cock test? A. 1. See that the test bottles and pipettes are accurately calibrated (accurately marked). 'i. See that the test bottles and pipette are clean. '■^. See that the centrifuge is properly oiled and in order before starting. i. See that the sample of milk to be tested is thoroughly mixed. (If a composite sample follow the details as explained below. ) o. See that the temperature of the sample oi milk is not below :)()° F. nor above 7<»° F. (). Measure out 17. (> cul:)ic centimeters of the milk with the pipette and put it into the test bottle. 7. See that the sulphuric acid is of the proi)er strength (sp. gr. l.S<; to 1.83). S. Measure out IT..') cc. of sulphuric acid and povir into the test bottle with the milk. !». Thoroughly mix the acid and milk. 10. Put the mixture into the centrifuge and see that the cen- trifuge is balanced. 11. Turn the centrifuge •"> minutes at the proper speed, then add hot water to the mixture until it reaches the base of the grad- uated neck. 12. Put into centrifuge and rotate the bottle two minutes more, li). Fill with hot water to 7 per cent, or A. By the same method as buttermilk except that only 10 cc. i)f acid is needed. DIVISION NINE. TESTING CREAM. Q. Is it of great importance for any farmer that produces milk to know how to test cream? A. It is very essential if he sells cream. Q. How may an accurate sample of cream be secured from the cream can? A. The cream should be warm enough to pour readily. When it is practical to do so the cream should be poured from one vessel to another, as in sampling milk, and a sample taken with a dipper. 30 TESTING CREAM Otherwise, a strong disc of tin or tinned metal, fastened to the end of a stiff rod long enough to reach to the bottom of the can, should be used for stirring. The upper portion of the cream is richer in fat than the lower, the same as in milk and the stirrer should be moved up and down until the upper and lower portions of the cream are thoroughly mixed. Thorough mixing cannot be too strongly emphasized. Care should also be taken to scrape from under the bulge of the can the heavy cream which collects there. If the disc used in stirring is concave the sample may be taken with it. Q. Are sampling tubes satisfactory for sampling cream? A. No. Q. Can frozen cream be sampled? A. Yes. If all the particles of ice are first melted. Q. Can churned cream be sampled? A. No. Q, Is it as satisfactory to take composite samples of cream as to test each sample separately? A. No. Because it is not usually convenient to take com- posites of cream proportionately or by aliquot parts. Q. Will the test of a composite sample of cream increase as it gets older? A. Yes. Unless very tightly stoppered and kept in a cool, place. The same is true of milk samples but does not amount to so much because of the smaller per cent, of fat. Q. Is the testing of cream by composite samples to be rec- ommended? A. No. Q. How is a cream sample prepared for testing? A. If cream is in good condition pour from one vessel to an- other. If it is thick warm slightly before pouring. If the sample is churned or has a tough layer on top, warm to 110° F. to melt butter fat, shake vigorously and cool to 60° F., continuing the shaking until cool. There is so much fat in cream that when it has once been separated it rises to the top too rapidly to sample accurately unless reincorporated as above. Q. How may sour cream be tested? A. It may be tested the same as sweet cream unless chunks of curd have formed. To destroy these it may be necessary to force the cream through a sieve, pressing the lumps through with the fingers. Q. How does testing cream by the Babcock test differ from testing imiilk? A. The cream must be accurately weighed instead of meas- ured. A special cream bottle is used. Less acid is required for •cream. The fat column is not read to the top of the upper meniscus. TESTING CREAM 31 Q.Why is it necessary to weigh cream? A. First, the Babcock test bottle has been so graduated that a sample to be tested should weigh 18 grams or a fraction thereof. Cream is lighter than milk, and thus a larger volume is required to weigh 1ample. Q. How is cream weighed for testing? A. (Jn a delicate balance, by dropping the cream from a pipette after the bottles have been balanced and the proper weight applied. Q. What is the construction of the special cream bottles? A. \'arious types are on the market. The most satisfactory are the nine-inch, nine-gram oO per cent., and the six-inch, nine- gram oO per cent, bottles. The difference between these two types is that the neck of one is longer than that of the other and there- fore smaller in diameter, making accurate reading of fat column less difificult. These bottles are built for using a nine-gram instead of an eighteen-gram sample, as in the whole milk bottle. In a nine-gram bottle a space representing 10 per cent, on the graduated portion will 'contain one-half as much as on the eighteen-gram bottle, or only 1 c.c. These bottles are graduated to one-half of one per cent. Another satisfactory bottle is the nine-inch, eighteen-gram, 30 per cent, crem bottle. As is indicated, this bottle is nine inches long" and is built for using eighteen-gram samples, the same as a whole milk bottle. This bottle is graduated to .2 per cent., the same as a 10 per cent, whole milk bottle. Six-inch, eighteen-gram bottles are used, but the fat column cannot be read with the same accuracy as in the bottles with longer necks. Q. Is it necessary to use 9 grams of cream in a nine-gram bottle and 18 grams in an eighteen-gram bottle? 32 TESTING CREAM A. No. Smaller amounts may be used. When less than 9 grams are used in a nine-gram bottle the fat reading is corrected by multiplying by nine and dividing by the size of the sample. Example — Suppose 6.5 grams of cream are used and the fat reading is found to be 30.5 per cent., then (30.5 X 9) -^ 6.5 = i'^.V per cent. When less than 18 grams are used in an eighteen-gram bottle, the same rule will hold, substituting 18 for 9. When a 1/2, 1/3 or l/-! sample is used in either case the fat reading is corrected by multi- plying by 2, 3 or 4 respectively. Q. How much acid is added to cream in testing? A. Use a little less acid than cream if no water is added. If a sample of cream smaller than 18 grams is used, best results are secured by adding enough cool water to make the total contents of the bottle approximately 18 grams and add acid as for milk. This lessens the danger of burning the fat and a clearer fat column is obtained than when no water is added. The bowls of some bottles are not large enough to add as much water as recommended above. It is an advantage to add at least a few c.c. in any case. A good rule is to add enough acid to produce a red-brown or coffee brown color when mixed. A rich cream does not need as much acid as a thin cream because there is more fat and a smaller amount of other solids. Too much acid will char the fat column and make the fat reading too low. Q. Can the cloudiness sometimes found in the fat column be overcome? A. Reshaking at the end of the first run, mixing the layer of fat with the acid will usually prevent this, provided the acid is of proper strength and the temperature in the tester is high enough.^ If the cloudiness is present at completion of the test, running an extra length of time in a steam heated tester will sometimes correct it, or the bottles may be set in cold water to solidify the fat,, then put in hot water to heat and melt it. and run again for a few minutes. Q, Is it possible to test cream in a whole milk bottle? A. Yes. By making a definite dilution by weight with water and multiplying the fat reading at the completion of the test, by the number of times the cream was diluted. The dilution must be great enough so that the fat may be read on the 10 per cent, scale. Q. How should the fat coluimn in a cream test be read? A. The most accurate reading is se.cured bv adding some colored glymol or white mineral oil to top of fat column, as sug- gested in Indiana Bulletin 145. This is best added just as bottles are taken from hot water bath to read. Tests should always be read from hot water bath at 140° F. The glymol is lighter than the fat and remains on the top of it, destroying the meniscus. If glymol is not used the reading should be taken at bottom of clear portion of upper meniscus. TESTING BUTTER AND CHEESE 33 Q. How is glymol prepared for use? A. In one quart of glymol suspend one ounce of crushed alkanet root wrapped in a piece of cheese cloth. In a day or two the glymol will absorb the red color from the alkanet root. The alkanet root can be secured from druggists. The glymol may be used uncolored but the line between the fat and the glymol is more distinct when the glymol is colored. DIVISION TEN. TESTING BUTTER AND CHEESE. Q. How many an accurate sample of butter for testing be secured? A. Take samples of uniform size from various parts of the churn or package. Place these in a vessel with tight cover. A glass stoppered bottle is best. Melt by holding the vessel in hot water. When butter becomes the consistency of thick cream and all lumps are gone, cool by holding under a stream of cold water and constantly agitating until it solidifies. The above operation furnishes a representative sample, which is uniform in composi- tion. The test sample is weighed from the resolidified mass. If one works quickly and carefully the test sample may be weighed from the melted sample by drawing it up in a pipette and weighing like cream. Great rapidity in manipulation is necessary to prevent error because the heavier material so quickly settles in the butter fat. Q. How is butter tested for butter fat by practical methods? A. (a) The most accurate one is that devised by Shaw, and reported in Circular "^OS, IJureau of Animal Industry. "Determination of fat alone. — The following apparatus is re- quired for the determination: A Babcock centrifuge, a special separatory funnel, a balance which is sensitive to .01 gram, an accurate set of metric weights, a 10-cubic centimeter graduated glass cylinder and a ino cubic centimeter glass beaker. Special separatory funnel. — This is essentially a separat(Try funnel with a, capillary stem. The capacity of the funnel should be about To cubic centimeters and its weight when empty should not exceed TO grams. The stopper may be dispensed with if desired. It is a convenience in the final weighing but not a necessity. Special socket. — Care must be taken that the capillary stem of the funnel does not project far enough through the hole in the socket to strike against the side of the centrifuge when being whirled. It is best to fit a disk of rubber gasketing to the bottom of the socket. T)etermining the fat. — It will be found more economical in some cases if 4: or multiples of 4 determinations are made at once. In this case the 2 double sockets containing the funnels will bal- 34 TESTING BUTTER AND CHEESE ance when placed opposite in the centrifuge. If but 1 or 2 deter- minations are to be made it will be necessary to balance the cen- trifuge by putting weights in the opposite socket. First of all the weight of the clean and dry separatory funnel must be ascer- tained, and this as well as the other weighings involved must be done with care. This weight once found will suffice for all deter- minations made with that particular funnel unless by accident some of the glass be chipped ofif. A slight scratch made with a file can serve to identify the funnels. A paper label cannot be used. I. Weighing the charge. — Counterpoise the small beaker on the balance and carefully weigh out 20 grams of the sample mixed as directed. II. I'ransf erring the charge to the separatory funnel. — The butter may be melted by adding a small quantity of boiling water. Next pour the charge into the funnel, which must be maintained in an upright position, and no part of the charge must be lost in transferring. With a. fine stream of hot water rinse down the sides of the beaker and pour the rinsings into the funnel. Repeat this, using not more than a teaspoonful of water at a time until the funnel is full to within one-quarter of an inch of the shoulder. In transferring the melted butter and rinsings the last drop may be prevented from running down the outside of the beaker by touching the lip of the beaker to the neck of the separatory funnel. III. Centrifuging. — Insert the separator}^ funnel in the spe- cial socket, allowing the stem to project through the hole in the bottom and the handle of the stopcock through the open side. ( Caution : The socket must always be placed in the centrifuge with the open side facing the direction in which the wheel re- volves. This is very important, for if the opening faces the re- verse direction the stopcock will be thrown out and broken.) Whirl one minute at the same speed used in testing milk with the Babcock test. The centrifuge must be kept warm. IV. Removing the water. — Remoi-^ the separatory funnel from the socket and allow the water to flow through the stopcock until the fat (or curd) is within one-eighth of an inch of the stop- cock. In this and subsequent operations involving the stopcock one must be sure it is under control or it may stick and the sam- ple be lost. Give it frequent slight movements when the water or acid is running through it to be sure that this control is main- tained; otherwise it might stick at a critical moment and the determination be lost. The most of the salt and part of the curd are taken out by the water. The remainder of the curd and all of the fat stays in the funnel. V. Dissolving the curd. — Measure out 9 cubic centimeters of cold water, preferably condensed steam, with the glass graduate and pour into the beaker. Add to this 11 cubic centimeters of sulphuric acid of the same strength used in testing milk and cream ( specific gravity 1.82 to 1.83) and mix by gently shaking. TESTING BUTTER AND CHEESE 35 (Caution: Always add acid to water and not water to acid, or a serious accident may result.) While still very hot add the mix- ture to the contents of the separatory funnel. Now dissolve the curd by giving the funnel a circular motion with the hand grasp- ing the neck. Centrifuge one minute, as before. Draw off the acid solution till the fat layer is within one-fourth of an inch of the stopcock. Repeat the operations in this paragraph. VI. Freeing the fat from the acid solution. — The fat will now be in a clear transparent layer free from curd, and the solu- tion below it will be practically colorless. To separate these two, draw off the latter until the fat nearly reaches the stopcock and centrifuge another mintue. Now allow the fat to come down through the stopcock till it just reaches the end of the capillary stem. This last step oft'ers no difffculties, providing the stopcock is kept in control, but it requires care. VII. Determining the percentage of fat. — Carefully dry the separatory funnel on the outside with a clean soft towel and weigh it. Tlie weight thus obtained minus the weight of the empty funnel represents the weight of butter fat in 20 grams of the sample. The percentage is obtained b}' dividing this weight by 2 and multiplying by 10. If there is a slight emulsion at the bottom of the fat column at the end of the operation it should be weighed as fat." (b) A special butter test bottle may be used. This has a double neck, one for adding butter and acid and one for reading" fat column. In using this bottle 9 grams of butter are weighed into it, 9 grams of water are added and 9 c.c. of acid. Proceed as usual with the Babcock test. It is difficult to secure an accurate test of butter by the Babcock test. Q. How is butter tested for moisture by the Irish method? A. Prepare sample as for testing for fat. Dry an aluminum cup over a gas or alcohol flame, the alcohol flame is better. Then balance on delicate scale. W^eigh into the cup ten grams of butter. Evaporate over the alcohol flame until all water is gone. This point may be determined by holding a small mirror over the cup. \A''hen moisture ceases to condense on the mirror, the evaporation is complete. The sediment in cup will also turn a slight brown and the crackling will cease. Reweigh the cup and calculate the per cent, of moisture driven off. The accuracy of this test depends on getting a fair sample of butter, careful weigh- ing and evaporating to just the correct point. Example — Suppose a 10-gram sample of butter is used in either the Irish or the Farrington oven test. On reweighing the loss of moisture is found to be 1.4 grams. Multiplv 1.4 bv 100 and 1.4 X 1<^<^ divide bv 10 or = 14 the per cent, of water in the butter. 10 Special moisture per cent, weights have been devised, which will determine the per cent, of moisture without calculation. These 36 TESTING BUTTER AND CHEESE are added to the side of the balance containing- the sample cup after the evaporation and the value of weights necessary to bring to original weight will show per cent, of moisture driven off. Q. How is butter tested for moisture by the oven method? A. Weigh into a shallow aluminum dish from lU to 50 grams of butter. The size of dish will govern the, size sample used. The larger the sample the less the chance for error. Place the dish in the oven. Turn on enough steam to give a temperature of 250° F. and leave until moisture is evaporated, which will usually be from 45 minutes to one hour. Reweigh and calcvtlate the per cent, of water from the loss in weight as in the Irish test. Q. What is the Ames-Cherry butter moisture test? A. The manipulation is the same as in the Irish test except that two aluminum cups are used, the one containing the butter sample sitting within the other during evaporation and the two sitting in a paraffine bath. The advantage claimed for this test is that the heating may be more easily controlled. Q. How may the per cent, of salt in butter be determined? A. Prepare butter sample as usual. A method devised by Vivian is as follows: Weigh 3.5 grams of butter on a small piece of parchment paper. Add butter and paper to 180 c.c. of boiling water in a flask and shake to dissolve the salt, removing the stopper frequently to release the steam. Let stand until cool. Then by means of an ordinary 17.6 c.c. pipette transfer 17.6 c.c. of the fat free liquid to a clean beaker or white cup. The pipette may be forced through the layer of fat wtithout any fat entering if the upper end is closed by placing the finger over it. If a separatory funnel is at hand the contents of the flask may be transferred to it before cooling and the salt solution drawn from it after the fat has risen. To the 17.6 c.c. of solution in the beaker add two drops of potassium chromate for indicator and then add a solution of silver nitrate from a burette until the contents of the beaker become red. The number of c.c. of silver nitrate solution used indicates the number of tenths of one per cent, of salt. For instance, if 35 c.c. of silver nitrate solution are used the per cent, of salt is 35 X -1 =: 3.5 per cent, of salt. The silver nitrate solution is prepared by dis- solving 1.018 grams of pure silver nitrate in 1 liter (1000 c.c.) of distilled water. Q. What is the melting test for distinguishing butter from process or revonated butter? A. Melt from 50 to 100 grams of butter or process butter at 120 degrees F"ahr. The curd from butter will settle, leaving a clear supernatant fat. The supernatant fat from process butter does not assume that clear appearance, but remains more or less turbid. Q. What is the boiling test for distinguishing oleomargarine and renovated butter from butter? TESTING BUTTER AND CHEESE 37 A. Alelt a small piece of the suspected material in a spoon or other small dish over a flame. Boil vigorously. Oleo and reno- \ated butter sputter and crackle noisily and form little foam, while butter makes little noise and much foam. The oil rising on melted ])Utter when allowed to stand is clear, while that rising on oleo and renovated butter is cloudy. Q. How may oleomargarine and renovated butter be dis- tinguished? A. Heat about one pint of sweet skim milk to about 14:0° F. Add about a teaspoc^nful of the material to be tested and stir until it melts. Then cool quickly by setting the cup in ice water and stir with a wooden spatula until the fat hardens. Oleomargarine will collect in a lump while butter and renovated butter will remain separated in small granules. Q. How is a cheese sample prepared for testing? A. Preparing sample. — As in butter great care is needed to secure sample representing average composition. A narrow wedge reaching from the edge to the center will do this. This should be cut quite fine with a sharp knife, taking care not to squeeze out moisture and fat, and thoroughly mix. If a plug is taken with a cheese trier it should be taken perpendicularly one-third of the wav from the edge to the center. It should reach completely through or only one-half way through. This should be cut and mixed in the same manner as the wedge. It is better when it can be done to take two or three plugs on dififerent sides of the cheese and mix the whole plugs or split them lengthwise and mix one-half of each. Q. How is cheese tested for butter fat? A. \\'eigh into a cream bottle 1.5 to (! grams of the chopped cheese. Add about 15 c.c. of hot water and shake until the cheese is dissolved. Keeping the bottles warm and adding a few c.c. of acid will sometimes hasten the process. When the curd is dis- solved add acid as for cream and proceed as in testing milk. To correct the reading multiply by 9 or IS depending on whether a ^) or 18-gram bottle is used and divide by the number of grams in .sample. Q. How is cheese tested for water? A. Prepare sample as in testing for fat. Weigh 10 grams of the prepared cheese into an aluminum dish. Place in an oven at a temperature of 250° F. for at least one hour or until weight is con- stant. Re weigh and calculate the per cent, of water from loss of weight as in testing butter for water. 38 ICE CREAM AND CONDENSED MILK DIVISION ELEVEN. TESTING ICE CREAM AND CONDENSED MILK. Q. How may ice cream be tested for butter fat? A. Eirst method. — The sample of ice cream should be melted and mixed by pouring from one vessel to another as with ordinary cream. Weigh 9 grams of the ice cream into a 10 per cent, or 8 per cent, whole milk bottle. Add a mixture of equal parts hydrochloric acid and glacial acetic acid until the bottle is tilled nearly to the neck. Mix and heat over a flame until the contents turn black. Place in centrifuge and proceed as with milk. Cor- rect reading by multiplying by 2. Second method. — Carefully weigh 18 grams of melted ice cream into an 18-gram cream bottle or 9 grams into a 9-gram bottle. Add 4 or 5 c.c. of lukewarm water. Next add commercial sulphuric acid, a small amount at a time. Thoroughly mix after each addition and allow some time for the acid to act Ijefore adding more. Continue this process until the contents of the bottle have become the color of strong coffee. Then add 4 or 5 c.c. of cool water to check further action of the acid. Usually from one-half to two-thirds the amount of acid used for ordinary cream will be sufficient. Complete the test as in an ordinary cream test. The success of this method depends largely upon the care in adding onlv small amounts of acid at a time and thor- oughly mixing after each addition. Q. How^ is unsweetened condensed milk tested for butter fat? A. Carefully weigh 4.o grams of well mixed evaporated milk into a 10 per cent, test bottle. Add one 17.6 c.c. pipette of water. Add 17.5 c.c. of sulphuric acid and shake until the curd is com- pletely dissolved. AA'hirl at usual speed for five minutes. Mix equal parts of water and sulphuric acid in a glass beaker and fill test bottle to zero mark, while the mixture is still hot. Whirl for two minutes in tester, fill bottles to 8 per cent, mark with hot water and whirl for one minute. Read tests from hot water bath, at temperature of 140° E. reading from bottom to top of fat column as in whole milk. Multiply reading by 4 to secure correct per cent, of fat.* Q. How may sweetened condensed milk be tested for butter fat? A. Transfer the contents of can to a beaker or evaporating dish and stir until homogeneous. Weigh 40 grams of the mixed sample in a 100 cubic centimeter flask, or transfer thereto by washing, and make up to the mark with water. After thorough mixing place 15 cubic centimeters of the 40 per cent, solution in a Babcock test bottle. Fill the bottle nearly to the neck with water, add 4 cubic centimeters of Eehling's copper solution (;14.()39 *Hunziker's method. TEST FOR CASEIN IN MILK 39 c.c. of copper sulphate dissolved in water), and shake thoroughly and rapidly. Separate the precipitated proteids by whirling- in a centrifuge for two minutes. A cold centrifuge is to he pre- ferred. AXithdraw- the supernatant liquid by means of a small stemmed pipette with a Avisp of wet absorbent cotton twisted over the bottom to serve as a filter. Wipe off the cotton into the bottle on withdrawing- the pipette. Give the contents of the bottle two additional washings by filling- the bottle nearly to the neck with water, centrifuging- and drawing oiT the supernatant liquid in same manner as above. The copper solution is not to be added in these additional washings. Finally add water to an approxi- mate volume of 17.5 c.c. and 17.5 c.c. of sulphuric acid and con- tinue the test as in the Babcock test for milk. Multiply the read- ing bv 3 for the percentage of fat in the sample. DIVISION TWELVE. TEST FOR CASEIX IN MILK. Q. How may the per cent, of casein in milk be determined? A. By the Hart test for casein. Q. What special apparatus is necessary for the Hart test for casein? A. A high-geared centrifuge which will give 2,000 revolutions per minute for a 15-inch wheel, a special test bottle, a 5 c.c. pipette for measuring the milk, a c\!inder for measuring the chloroform. Q. What principles are involved in performing the test? A. The casein of the milk is precipitated by a dilute solution of acetic acid. Chloroform is used to extract the fat and make a solution heavier than the milk serum. Centrifugal force is used to separate the chloroform containing the fat, the casein and the milk serum into three separate layers. Q. How is the acetic acid solution prepared? A. It must be a .'?5 per cent, solution. Add 10 c.c. of pure glacial acetic acid to W c.c. of distilled wiater, making 100 c.c. of solution. To 25 c.c. of this solution add 975 c.c. of distilled water, making 1000 c.c. This will be a .25 per cent, solution. Q. How is the Hart casein test made? A. The temperature of the milk and acetic acid must be be- tween 65° and 75° F., 70° F. being the temperature desired. The correct temperature is very important, a low temperature giving too high a reading of casein and a high temperature giving too low a reading.l The "room should be near 70° F. in temperature. To the special test bottle add 2 c.c. of best chloroform, then 20 c.c. of the acetic acid solution and last 5 c.c. of milk accurately measured. As soon as the materials are in the bottle, place the thumb over the opening, invert and shake somewhat vigorously for no less than 15 seconds and no more than 20 seconds. Place the bottles in the 40 STANDARDIZING contrifuge and whirl at 2,000 revolutions per minute for a lo-inch wheel for eight minutes. The chloroform with the fat should then be found in the bottom of the test bottle, the layer of white casein next and on lop the acetic acid and milk serum. Allow the bottles to stand in an upright position for 10 minutes before reading-. Q. How may the per cent, of casein in milk be calculated when the per cent, of fat is known? A. By the following rule devised by V^an Slyke : Subtract 3 from the per cent, of fat in the milk, multiply the remainder by .4 and add 2.1 to the result. Example. — Suppose the milk contains 4.3 per cent, of fat. Then (4.3 — 3) X -4 + 3.1 = 2.63 per cent, of casein. This rule is based on the assumption that milk containing 3 l)er cent, of fat contains 2.1 per cent, of casein and that for each 1 per cent, increase in the fat, the casein increases .4 per cent. It is fairly accurate only when the fat ranges from 3 to 4.5 per cent. In the later stages of lactation the ratio of casein to fat is apt to 1)6 greater than indicated by this rule. DIVISION THIRTEEN. STANDARDIZING MILK AXD CREAM. Q. What is meant by standardizing milk or cream? A. To standardize milk is to bring the butter fat content to a given per cent, regardless of the quality of milk produced by the cow. If the milk as drawn from the cow contains less butter fat than is desired, it can be brought to the desired standard by add- ing cream or extracting some skim-milk. If, on the contrary, milk that is yielded by the cow contains more butter fat than is neces- sary, it can be reduced to the desired standard by extracting cream or adding skim-milk. Q. Is it just to standardize milk? A. Yes, because the producer can not afiford, for example, to ])roduce milk containing five per cent, butter fat and receive pay for milk which contains only four per cent, butter fat (providing it is produced under equal sanitary conditions). To be legitimate the per cent, of fat must be indicated on the container. Q. Can not this reduction of fat be secured by the addition of water? A. Yes. But this is not permissil)le. for it also reduces the percentage of the solids not fat ; that is, casein, milk sugar, and ash ; whereas standardizing with cream or skim-milk does not materially alter the proportion of solids other than butter fat. Q. Is there a definite standard to which milk or cream is standardized ? A. The butter fat in milk or crean) is increased or decreased to an arbitrary per cent, or standard which may be fixed by law or an agreement between parties in which one guarantees to furnish STANDARDIZING 41 the other with a definite quantity of butter fat in eevry pound of milk or cream sold for a stated price. This price should vary with the per cent, of butter fat in the milk — the more butter fat for the same quantity of milk the higher the price, and vice versa. Q. How can the fat in milk or cream be reduced? A. If milk contains a higher per cent, of butter fat than is de- sired, this fat can be reduced either by separating the cream out of a portion of the milk or by adding skim-milk. In case all the milk is separated for clarification, the same result may be obtained by mixing with the skim-milk a smaller portion of the cream than was contained in the original milk. Again, there may be an in- stance in which no skim-milk is on hand, but instead, an ample supply of milk with a lower per cent, of butter fat than is desired. This milk will answer the same purpose as skim-milk, but a larger proportion is required to bring the per cent, down to the proper standard. Q. How can the fat in milk or cream be increased? A. Milk of a lower per cent, of fat than is desired may be standardized by taking out a portion of the skim-milk by means of a separator, or by adding reserved cream ; or, as in the above case, if the milk is separated for clarification, by mixing with the skim- milk a greater portion of cream than there was in the original milk. Here, as in the above instance, if circumstances should arise in which there is no cream on hand, but instead, milk of a higher per cent, of butter fat than the desired standard, this will then answer the same purpose for increasing the percentage of fat to the proper standard. Q. How can you determine the amount of skim-milk to be added or removed from the whole milk to obtain the desired per cent, of butter fat? A. According to the following rules : Rules for Standardizinfy Under Different Conditions Are as Follows: Rule I. Multiply the number of pounds of milk by the per cent, of fat in the milk alid the product will be the number of pounds of but- ter fat in the milk. Divide the number of pounds of butter fat in the milk by the decimal representing the desired per cent, of fat, and the quotient will be the number of pounds of standardized milk.''' *This answ^er is sufficiently accurate for ordinary practice. A?^ a matter of fact, the amount of butter fat in the cream to be stand- ardized is less than the amount of butter fat in the milk, on account of some butter fat left in the skim-milk by separating. Agairu when skim-milk is added, butter fat is also added, the amount de- pending iipon the amount of skim-milk added and the per cent, of fat contained therein. 42 STANDARDIZING Part 1. Where the Percentage of Fat is too High. — From the number of pounds of standardized milk take the number of pounds of original milk and the result will be the number of pounds of skim-milk to be added to the original milk. To illustrate: 1000 pounds of milk containing- 4.5 per cent, of butter fat are to be standardized to 4 per cent. : how many pounds of milk must be added? Since 4.5 per cent, equals the decimal .045 then. 1000 X -045 = 45, the number of pounds of fat in iniio pounds of 4.5 per cent. milk. 45 -^ .04 = n'?5. tlie number of pounds of 4 per cent, or stand- ardized milk. 1125 — 1000 =: 125, the amount of skim-milk to be added. To formulate this problem : A : 1000 : : 4.5 : 4 A — .- the pounds of standardized milk. 1000 X 4.5 B = 1000 4 B =^ the number of pounds of skim-milk to be added. Part 2. Where the Percentage of Fat is too Low. — W ith milk that is to be standardized from a h^wer to a higher per cent, the same rule holds true ; but in this case take the number of pounds of standardized milk from the number of pounds of original milk and the result will be the number of pounds of skim-milk to be removed from the original milk. To illustrate: 1600 pounds of milk containing 3.2 per cent, of butter fat are to be standardized to 4 per cent. ; how much skim- milk must be taken from the whole milk? 1600 X -O^S = 51.2, the number of pounds of butter fat in the original milk. 51.2 -:- .04 = 1280, the number of pounds of standardized milk. 1600 — 1280 r= 320, the number of pounds of skim-milk to be separated from the' original milk, or 1600 X 3.2 A = — 1280. 4 A = the number of pounds of standardized milk. B = 1600—1280 = 320. B = the number of pounds of skim-milk to be removed. Rule II. The same results may be reached by the following rule, which is often more convenient than the one above gi\'en. Divide the* per cent, of butter fat that is in the original milk In' the per cent. that is desired in the standardized milk. The quotient multiplied by the given numl)er of pounds of milk will be the amount of standardized milk. If the quantity of standardized milk is greater than the original amount of milk the diiference must be added in STANDARDIZING 43 the form of skim-milk; if less, then that difference must be sepa- rated out as skim-milk. Part 1. Where the Percentage of Fat is too High. — To Illus- trate : ■.'•>() pounds of milk containing 6 per cent, of fat are to be standardized to 4 per cent.; how many pounds of skim-milk must be added? .0(j -^- .O-i := 1.5. hence 200 pounds of 6 per cent, milk must be increased by one-half with skim-milk, or to 300 pounds. The dif- ference between 200 pounds and 300 pounds is the amount of skinv milk that must be added, or .0(5 A = — X 200, in which A = final amount of standardized milk. M Part 2. Where the Percentage of Fat is Too Low. — To illus- trate : (552 pounds of milk containing 3.1 per cent, of butter fat are to be standardized to 4.5 per cent. ; how many pounds of skim- milk must be extracted? 3.1 -!- 4.5 ^ .691, or the fractional part of 652 pounds of 3.1 per cent, milk to which the amount must be reduced in order to have the milk contain 4.5 per cent, butter fat. 652 X .691 =: 450. the number of pounds of 4.5 per cent. milk. 652 — 450 ^= 202, the number of pounds of skim-milk to be removed, or 3.1 A := — X fi-">2, in which A =: final amount of standardized milk. 4.5 Rule III. Occasionally there may be a quick demand for milk of a per cent, of fat which is not commonly produced, as is often the case with city dairy companies. However, milk of a known standard is always on hand. In this case a definite quantity of milk is wanted and the exact proportions of milk or cream to be added to the skim-milk may be calculated in percentage or amount as follows : Divide the per cent, of fat in the milk that is desired by the per cent, of fat in the milk that is on hand. The result will be the per cent, of the milk on hand to be taken ; the remaining per cent, of milk will be the skim-milk to be used. To illustrate: 120 pounds of milk containing 4 per cent, of butter fat is desired and milk of 6 per cent, fat and skmi-milk are on hand, to be used. What per cent, of the standardized milk must be milk with 6 per cent, fat and what portion must be skim-milk: t^^at is, how much of each must be taken in order that the mixture may be 4 per cent, milk? .0-1 ^ .06 = .66 2/3 or 66 2/3 per cent., which is the portion of 6 per cent, milk that the 120 pounds of standardized milk should contain. The remaining 33 1/3 per cent, must be skim-milk which "t is necessarA- t(^ add to bring the fat down 4 per cent. 44 STANDARDIZING GO 2/0 per cent, of 120 pounds — 80 pounds, the amount of ii per cent, milk which must be mixed with 40 pounds of skim-milk to bring- the mixture to 120 pounds of 4 per cent. milk. Rule IV. Part 1. — The actual number of pounds instead of the per cent. of the different kinds of milk to be added may be ascertained as follows : Multiply the number of pounds of standardized milk de- sired by the per cent, of butter fat that the milk is to contain. This gives the number of pounds of butter fat in the mixture. Divide this amount by the per cent, of butter fat contained in the milk on hand and the result will be the number of pounds of that milk which the standardized milk should contain. The remainder would be skim-milk. To illustrate : 50 pounds of milk containing" 3 per cent, fat is wanted, and milk containing' 5 per cent, fat is to be used. 50 X -03 := 1.5, the number of pounds of butter fat in the 3 per cent. milk. 1.0 -^- .05 = 30, the number of pounds of 5 per cent, milk which the standardized milk should contain. 50 — 30 = 20, the number of pounds of skim-milk to be added. Part 2. — In case there is no whole milk on hand but instead skim-milk and cream of a known per cent, of butter fat, then the ■cream may be substituted and the fat reduced to the desired per cent, with skim-milk. The proportionate amounts may be calcu- lated as in the two foregoing methods. To illustrate : To make 50 pounds of milk containing 3 per •cent, of fat or 1.5 pounds of butter fat as in the above illustration. If 25 per cent, cream is to be substituted for 5 per cent, milk then the standardized milk would have to contain 6 pounds of 25 per cent, cream and -H pounds of skim-milk. As a matter of convenience the results of the above rules cal- culated on the per cent, or 100 pound basis can be tabulated in such a manner as to reduce the calculation to a minimum. Table 1 Indicates Quantity of Skim-Milk to be Added to or Sub- tracted from 100 Pounds of Milk to Make the Desired Per Cent. *A 3.25 3.50 3.75 4.0 1.25 4.50 4.75 5.0 tB 3.0 — 7.693 —14.285 —20.000 — 25.000 —29.412 —33.333 —36.842 —40.000 3.1 — 4.016 —11.423 — 17.333 —22.50 —27.059 —31.11] —34.737 —38.000 3.2 — 1.539 — S.57':l — 14.666 — 20.000 — 24.7i)6 — 28.888 —32.632 —36.000 3.3 -f 1.539 — 5.714 —12.000 —17.50 —22.353 —26.666 —30.527 — 34.000 3.4 + 4.616 — 2.857 — 9.333 — 15.00 —20.000 —24.444 28.422 — 32. (>()() 3. .5 4- 7.693 — 0.000 — 6.666 —12.50 —17.647 22.222 —26.317 — 30.000 3.6 -f-10.760 -h 2.857 — 4.000 —10.00 —15.294 —20.000 —24.212 — 28.000 3.7 -1-13. S37 + 5.714 — 1.333 — 7.50 —12.941 —17.777 —22.107 — 26.000 :3.8 -1-16.914 -\- 8.571 + 1.333 — 5.00 — 10.5SS —1 5.555 —20.000 — 24.000 *Top line A represents the per cent, of fat that is desired in milk. fLeft-hand column B represents the per cent, of fat in milk on handi STANDARDIZING 45 *A 3.25 3,50 3.75 4.0 4.25 4.50 4.75 5.0 tB 3.9 +19.991 +11.428 + 4.000 — 2.r>Q — 8.23.5 —13.3:53 — 17.897 — 22.000 4.0 +23.068 +14.285 + 6.666 — 0.00 — .5.882 —11.111 — 15.792 —20.000 4.1 +26.145 +17.142 + 9.333 + 2.50 — 2.429 — 8. 888 — 13.687 — 18.000 4.2 +29.222 +19.999 +12.000 + 5.00 — 0.076 — 6.666 —11.582 — 16.000 4.3 +32.299 +22.856 +14.666 + 7.50 + 0.076 — 4.444 — 9.477 —14.000 4.4 +35.376 +25.713 +17.333 +10.00 + 2.429 — 2.222 — 7.372 —12.000 4.5 +38.543 +28.57 +30.000 +12.50 + 5.882 — 0.000 — 5.267 —10.000 4.6 +41.530 +31.427 +22.666 +15.00 + 8.235 + 2.222 — 3.162 — 8.000 4.7 +44.607 +34.284 +25.333 +17.50 +10.588 + 4.444 — 1.057 — 6.000 4.8 +47.684 +37.141 +28.000 +20.00 +12.941 + 6.666 + 1.057 — 4.00O 4.9 +50.761 +39.998 +30.666 +22.50 +17-647 + 8.888 + 3.162 — 2.000 5.0 53.838 42.855 33.333 25.000 20.000 11.111 + 5.267 — O.OOO *Top line A represents the per cent, of fat that is desired in milk. tLeft-hand column B represents the per cent, of fat in milk on hand. To find the pounds of skim-milk to be added or removed, trace the vertical column of the per cent, of fat you desire down to where the horizontal column representing the per cent, of fat in the milk on hand intersects and the result will be the number of pounds of skim-milk to be added or removed, as indicated by a plus or minus sign before the result. To illustrate : If milk containing 4.5 per cent, is desired and milk containing 3.8 per cent, fat is on hand, then 15.5 pounds for every hundred pounds or 15.5 per cent, of the quantity must be separated out as skim-milk. To Standardize with Whole Milk or Cream Instead of Skim-Milk. Rule V. Part 1. — An instance may occur in which milk is to be raised to a higher per cent, with milk of a still higher per cent, of butter fat. The quantity to be added may be found in the following man- ner : From the desired per cent, of fat in the standardized milk subtract the per cent, of fat in the milk that is on hand which con- tains the lower per cent, of fat. Subtract the per cent, of fat that is desired in *milk from the per cent, of fat in the milk that is on, hand which contains a higher per cent, of butter fat. Divide the difference between the lower per cent, and the per cent, desired by the dift'erence between the higher per cent, and the per cent, de- sired. The quotient will be that part of any given quantity of milk containing the higher per cent, that should be taken. [Multiply the quotient by the quantity of milk of the lower per cent. This will equal the quantity of milk of the higher per cent, to be added to the milk of the lower per cent, and the sum will equal the amount of the mixture containing the desired per cent. To illustrate : Standardize 20 pounds of milk containing 3 per cent, butter fat to 4 per cent, fat with 5.2 per cent, milk; how many 46 STANDARDIZING pounds of the latter must be added to bring the fat up to 4 per cent. ? .04 — .03 = .01. .052— .04 = .012. .01 -:- .012 = .833. 200 X -833 =r 166.6, the number of pounds of 5.2 per cent, milk to be added. 200 -(- 166.6 = 366.6, the number of pounds of 4 per cent, milk to be used. Part 2. — To standardize milk of a higher per cent, than is de- sired with milk of a lower per cent, of fat, the same rule applies except that the difTerence between the desired per cent, and the higher per cent, must be divided by the difference between the de- sired per cent, and the lower per cnt. of butter fat. To illustrate : 54 pounds of milk containing 5.3 per cent, of butter fat are to be standardized to 4 per cent, with milk contain- ing 3.1 per cent, butter fat ; how many pounds of the 3.1 per cent, milk will be required? .053 — .04 — .013. .04 — .031 = .009. .013 ^ .009 = 1.44. 54 X 1-44 := 77.76, the number of pounds of milk containing 3.1 per cent, of fat to be added to the 54 pounds to decrease the fat content to 4 per cent. Rule VI. To find the ratio of the number of pounds of milk of the differ- ent per cents., subtract the per cent, of fat in the milk of the lower fat content from the per cent, of fat desired in the standardized milk and divide this result by the difTerence between the fat per cents in the milk of the higher fat content and the lower fat con- tent, the quotient represents the per cent, of milk of the higher fat content to be used in standardizing. To illustrate : Find the ratio of the pounds of milk for mixing 5 with 3.5 to give 4 per cent. milk. 4 — 3.5 — .5. 5 — 3.5 = 1.5. .5 ^ 1.5 = .33 1/3 or 33 1/3 per cent., which is that part of the standardized milk containing 5 per cent., which is used in mixing with milk of 3.5 per cent, fat content. Supposing 400 ^pounds of milk of 4 per cent, butter fat is desired then 33 1/3 per cent, of the 400 pounds or 133.3 pounds are to be milk containing 5 per cent, butter fat and 400 — 133.3 = 266.6, the number of pounds of milk of 3.5 per cent, butter fat that are to be taken to bring the fat con- tent to 4 per cent. Where whole milk is used for standardizing the results can be tabulated equally as well as when skim-milk is used. In this case the whole milk has a constant per cent, in each table. i; 20 22 25 27 30 50.0000 61.5385 69.2308 80.3461 88.4615 100.00 9 2.8 5: 86.666 81.250 100. 76A70ii 94.706 72.2222 88.8888 100. 68.4232 84.2222 94.2125 65.0000 80.0000 90.0000 61.905 76.1905 85.7143 100. 59.0909 72.7272 81.8181 95.4545 56.5217 69.5651 78.2608 91.3044 100. 54.1666 66.6666 75.0000 87.5000 95.8333 52.0000 64.0000 72.0000 84.0000 92.0000 50.0000 61.5385 69.2308 80.3461 88.4615 100.00 STANDARDIZING " 47 Table 2. To Standardize Cream with Milk Containing 4 Per Cent, of Butter Fat. -A tB 30 18 19 20 21 2 2 23 24 25 26 27 28 29 .:50 *A represents the per cent, of fat that is desired in cream. ILett hand column B represents the per cent, of fat in cream .'Ml hand. If cream is to be standardized with whole milk the result found b}' the intersecting columns represents the pounds per hun- dred or the per cent, of the quantity which is cream of the per cent, of fat on hand. To illustrate : If cream containing" 20 per cent, of butter fat is desired and cream containing" 26 per cent, of butter fat is on hand then 72.1 per cent, of the quantity desired must be cream contain- ing 26 per cent, of butter fat and 27.3 per cent, of the quantity must be 4 per cent. milk. Q. How is cream standardized? A. The principal diii'erence between milk and cream is that in cream a larger portion of the water is displaced with butter fat and since the variations lie mainly between the butter fat and the water the same methods that apply to the standardization of milk will apply to the standardization of cream. Q. What apparatus is necessary for standardizing? A. The apparatus necessary for standardizing" milk or cream is a cream separator, a Babcock tester, scales, and a mixing" vat. Q. What is the parallelogram method of standardizing? A. It is a method devised by Professor Pearson, formerly of Cornell, and may l^e illustrated as follows: A i^ ■ 1 C — B or B — C A or A — B 4S STANDARDIZING A Per cent, of fat in milk to be mixed. B Per cent, of fat in standardized milk C. Per cent, of fat in cream or milk to be mixed with A. C — ■ B or B — C Pounds of A to use. B — A or A — B Pounds of C to use The per cent, of fat desired in the standardized mixture is always placed in the center of the parallelogram and the per cents of fat in the milks to be mixed at either of the two left hand cor- ners. Then subtracting diagonally we secure the proportions of A and C to be mixed to secure mixture containing per cent, of fat indicated by B. In other words A — B or B — A depending on which is the larger, will give the number of pounds of C to Y- taken for the mixture. In like manner B — C or C — B will show the number of pounds of A to be taken for the mixture. The prob lems in the following questions will illustrate the method. Q. How imuch cream containing 30 per cent, of butter fr must be added to 500 pounds of milk containin.cr 3 per cent, of but- ter fat to standardize it to milk containing 5 per cent, of butter fa A. 3 •?:) (30 — 5) 2 (5 — 3) Placing the per cent, of fat desired in the standardized milk in the center of the parallelogram and the per cents of fat in the materials to be mixed at the left hand corners and subtractin-^ diagonally we have 30 — 5 =: 25 and 5 — 3 =: 2. This means that the milk containing 3 per cent, of butter fat and cream containin 30 per cent, of butter fat must be mixed in the proportion of 25 to 2 or 121/2 to 1, to produce milk containing 5 per cent, of butte" fat, that is for every 25 pounds of milk containing 3 per cent of butter fat in the mixture there must be 2 pounds of cream con- taining 30 per cent, of butter fat. Therefore, 25 : 2 : : 500 : x = 40 pounds of cream containing 30 per cent, of butter fat to add or 2 X 500 = 40 or (2 X 500)"^ 25 = 40. Q. How^ much milk containing 3 per cent, of butter fat and how much cream containing 30 per cent, of butter fat are to be mixed to secure 500 pounds of milk containing 5 per cent, of but- ter fat? ^A. ( See the parallelogram above, since the figures are the same.) 25 + 2 = 27. 27 : 25 :: 500 : x ^= 462.96 -|- pounds of milk containing 3 per cent, of Ijutter fat. BUTTER-FAT EQUIVALENT 49 27 : 2 :: 500 : x ^ 37.01 — pounds of cream containing" 30 per cent, of butter fat. Q. How much milk containing 3 per cent, of butter fat must be added to 500 pounds of cream containing 30 per cent, of butter fat to reduce the test to 25 per cent.? A. 30! 22 (25 — 3) 5 (.30 — 25) The cream containing 30 per cent, of butter fat and the milk containing 3 per cent, of butter fat must be mixed in the propor- tion of 22 to 5 ; or, for every 22 pounds of cream containing 30 per cent, of butter fat 5 pounds of milk containing 3 per cent, of butter fat must be used. Therefore, 22 : o :: 500 : x = 113. (i3 pounds of milk containing 3 per cent, of butter fat to be added. 500 X 113.63 =: 613. (i3 total number of pounds of cream con- taining 25 per cent, of butter fat secured. QL How much skim-milk containing .1 per cent of butter fat should be added to 1000 pounds of milk containing 5.5 per cent, of butter fat to reduce the test to 3.5 per cent.? A. 3.4 (3.5 .1) 2 (5.5 — 3.5) The proportion should be 3.4 to 2 or 3.4 pounds of the milk containing 5.5 per cent, of butter fat to 2 pounds of the skim-milk containing one-tenth of one per cent, of butter fat. If it is desired to consider the. skim-milk as containing no fat this can be done by using in the same manner as .1 in the above example. Therefore 3.4 : 2 :: 1000 : x = 588,23 pounds of skim-milk to add. 1000+ 588.23 = 1588.23 pounds of milk containing 3.5 per cent, of fat. . Q. Howmuch milk containing 5.5 per cent, of butter fat and how much skim-milik containing one-tenth of one per cent, of but- ter fat will be needed to produce 1000 pounds of milk containing 3.5 per cent, of butter fat? A. (See parallelogram above.) 3.4 + 2 = 5.4. 5.1 : 3.4 :: lOdO : x z= ()29.6 pounds of milk containing 5.5 per cent, of butter fat. 1000 — 629.6 = 370.4 pounds of skim-milk containing one- tenth of one per cent, of butter fat, or 5.4 : 2 : : 1000 : x ^= 370.4 pounds of skim-milk containing one- tenth of one per cent, of butter fat. 50 BUTTER-FAT EQUIVALENT Q. How much skim-milk containing one per cent, of butter fat must be removed from 780 pounds of milk testing 3 per cent, of butter fat to incr^ease the test to 4 per cent.? A. 3 3.!) pounds of milk containing" o per cent of butter fat to use. 1 pound of skim-milk to remove from I3.i) pounds of milk con- taining 3 per cent, of butter fat. Place the per cent, desired in the center of the parallelogram as usual, the per cent, of fat in milk on hand at upper left hand corner and per cent, of fat in skim-milk at lower left hand corner. Subtract diagonally as usual. The difference between the per cent, of fat desired and the per cent, in the skim-milk will indicate the number of pounds of milk containing 3 per cent, of butter fat to use and the difference between the per cent, of fat desired and the milk to be skimmed will indicate the number of pounds of skim- milk to remove. In this problem from every 3.9 pounds of milk containing 3 per cent, of butter fat 1 pound of skim-milk must be removed to increase the per cent, of fat to 4. Therefore. 3.S> : 1 : : 780 : x = 200 pounds of skim-milk to remove, or 1 X <8<> = 200 pounds of skim-milk to remove. 7S0 — -^OO = 5(S0 pounds of milk containing -t per cent, of but- ter fat. Q. How much milk containing 3 per cent, of butter fat will be required to produce 780 pounds of milk containing 4 per cent, of butter fat? A. (See the diagram above.) ' The 780 pounds of milk containing 4 per cent, of butter fat will be the number of pounds of milk containing 3 per cent, of butter fat less the number of pounds of skim-milk removed. Since 3.9 represents the amount of milk to use and 1 the skim-milk re- moved, 3.9 — 1 or 2.9 will represent the 780 pounds of milk con- taining 4 per cent, of butter fat. Therefore, we have the propor- tion :' 2.9 : 3.9 : : 780 : x = 1048.96 pounds of milk containing 3 per cent, of liutter fat to make 780 p(uinds of milk containing" 4 per cent, of butter fat ; or 3.9 X 780 ,-. = 1048.90 pounds of milk containing 3 per cent, of 2.9 butter fat to make 780 pounds of milk containing 4 per cent, of butter fat. BUTTER FAT EQUIVALENT 51 DIVISION FOURTEEN. RULES FOR CALLT'LATING BUTTER-FAT EOUIVALEXT IN DIFFERENT PRODUCTS. Q. How can the price per gallon of cream equivalent to the price of butter fat be found? A. ]\Iultiply the pounds of cream per gallon by the per cent. of butter fat in the cream, the product will equal the pounds of fat per gallon of cream. Divide the number representing the price per gallon of cream by the number of pounds of butter fat, the quotient will equal the price per pound of butter fat. To illustrate : W hat is the price per pound of butter fat if cream containing 20 per cent, of fat sells for 50 cents per gallon? A gallon of 20 per cent, cream weighs approximately 8.4 pounds. 8.4 X -20 = 1.08 the pounds of butter fat in one gallon which is worth 50 cents. $.50^1.68^$.-?!):, the price of one pound of butter fat. Q. How can the price per gallon of cream at a certain price per pound of butter fat be found? A. Multiply the pounds of cream per gallon by the per cent. of fat in the cream, the product will be the number of pounds of butter fat in one gallon of cream. Multiply this product by the ])rice per pound of butter fat you desire, -the product will be the price per gallon for cream. To illustrate : At o2 cents per pound of fat what would be the price per gallon of cream containing 27 per cent, of butter fat? 8.3 X -27 = 2.241 pounds of fat in 1 gallon. 2.241 X 32 = T1.T12, or T2 cents, the price of the 21 per cent, cream. Q. How can the equivalent price per gallon for cream con- taining different per cents, of butter fat be found? A. This is best calculated on a basis of proportion. Divide the means by the extremes. To illustrate : If cream containing- 20 per cent, of l)Utter fat is worth 60 cents per gallon what is cream wortli containing 25 ])er cent, of butter fat? .20 : .25 :: (iO : x GO X •'^'i = 1-5 15 ^ 20 = T5. or 7 5 cents, the equivalent worth of 25 per cent, cream in comparison to the worth of 20 per cent, cream at (50 cents a gallon. DIVISION FIFTEEN. DETECTION OF ADULTERATION IN MILK. Q. How can adulteration of milk with water be detected? A. Bv means of the lactometer. The Ouevenneis the best. 52 DETECTION OF ADULTERATION since it has a scale corresponding" to the specific gravity of milk. The graduated scale from 15 to 40 being equivalent to a specific gravity of 1.015 to 1.040 ; thus a milk which has a specific gravity of 1.032 would show on the lactometer a reading of 32. The upper scale of the lactometer is a thermometer scale. These lactometers are to give the specific gravity at a temperature of 60° F., and as it is not always convenient to have the temperature of the milk • at 60° F., when the reading is taken, corrections may be made for slight variations (not more than 10°) by adding to the lactometer reading .1 (1/10) for each degree of temperature above 60° F. or "subtracting .1 for each degree below 60° F. For example, the lac- tometer reading is 29 and the temperature 68° F., then the correct reading for 60° F. would be 29 -4- .8 r= 29.8. Had the temperature been 56 degrees, the correct reading would be 29 — .4 ^ 28.6, and the specific gravity would be 1.0286. The specific gravity is ob- tained by prefixing 1.0 to the corrected lactometer reading. The reading of pure milk ranges from 28 to 34. of skim-milk from 33 to 36, and the specific gravity of pure milk from 1.028 to 1.034 and of skim-milk from 1.033 to 1.036. The average composition of milk is as follows: Water 8? to 88 per cent. Fat 3.0 per cent, and upwards Solids not fat 8.5 to 9.5 per cent. Q. What is the function of the lactometer? A. The lactometer compares the weight of milk with the weight of an equal volume of water. Milk becomes heavier as the per cent, of solid not fat increases. Fat being lighter than water causes an error which must be taken into consideration. Q. What precautions are necessary in taking a lactometer reading? A. (1) Milk should stand at least one hour after milking to allow escape of gases. (2) The temperature must be between 50° and 70° F. (3) Milk should be mixed just before the reading but in such manner as not to cause froth or foam. (4) Milk should be placed in a cylinder and lactometer carefully lowered into it and let stand for 30 seconds and not more than one minute. (5) Read lactometer scale at level of milk and take thermometer reading". (6) Readings to one-half a lactometer degree are close enough. Q. How is the per cent, of solids not fat calculated? A. The next step to be taken is to determine the per cent, of fat, which is done by means of the Babcock tester. Then, having" obtained the per cent, of fat and the lactometer reading, the per cent, of solids not fat mav be. calculated bv the following formula: L+F ■ = per cent, of solids not fat. 4 L. Lactometer reading at 60°. F. Per cent, of fat. DETECTION OF ADULTERATION 53 \Miile the above formula is most convenient and is satisfactory for all practical purposes a more accurate formula is as follows: L 1~ -'-F =^ per cent, of solids not fat. 4 I.. Lactometer reading' at 60°. F. Per cent, of fat. Q. How is the per cent, of total solids calculated? A. By adding the per cent, of fat and the per cent, of solids not fat. Q. How can the per cent, of foreign water contained be determined? To find the extent to which a known sample of milk has been watered, multiply the per cent, of solids not fat in the adulterated sample by 100, and divide by the per cent, solids not fat in pure sample. The result will be the number of pounds of pure milk in 100 pounds of the sample examined, and the remainder will be the number of pounds of water. Pure milk contains not less than 8.5 per cent, solids not fat, and often as high as 9 and 9J^ per cent., and where it is not possible to get a sample of the pure milk for testing, use S.5 as a standard for the first half of the season and gradually increase to 9 as the season advances and as the period of lactation advances. To make the foregoing more plain, take the following- example : Lactometer reading 28, temperature 54°, per cent, fat 2.6, and' suppose the pure milk to test 9 per cent, solids not fat. Find the per cent, of water added. The correct lactometer reading is 28 minus .6, or 27. 4. Substi- tuting for formula we have : '.5 per cent, solids not fat; then 27.4 4- 2.6 = 7.5 X 100 30.0 4 750 8.3.3 per cent, pure milk: 9 . 9 then 100 — • 83.3 = 16.6 per cent, water in the adulterated sample. Q. What is the specific gravity of the solids of milk? A. From 1.25 to 1.34 for whole milk. The specilic gravity of the solids of completely skimmed-milk is about 1.56. Q. What does the specific gravity of the milk solids indicate as to skimming and watering of milk? A. When the specific gravity of the milk solids is above 1.34, skimming is to be suspected and w'hen it is above 1.40 it is con- clusive. Q. How may the specific gravity of milk solids be determined? 54 DETECTION OF ADULTERATION. A. By the following formula : t S — ^— 100s — 100 s S, the specific gravity of the milk solids ; s, that of the milk, and t, the total solids of the milk. Example. — Suppose the total soldis of a milk were found to be 13 per cent, and the specific gravity of the milk 1.082. Then, (100 X 1.032) — 100 '■ = 3.101 ; 13.0 — 3.101 = 9.899 ; 1.032 13 ^=. 1.31, the specific gravity of the milk solids. 9.S99 Q. When is adulteration by skimming indicated? A. When the lactometer reading is 33 or above and the per cent, of fat is 3 or below, or when the lactometer reading, the specific gravity of the milk and the per cent, of solids not fat are high and the per cent, of fat is low. The specific gravity of the milk solids is high in skim-milk. Q. When is adulteration by watering indicated? A. \Mien the lactometer reading is 28 or below and the per cent, of fat is correspondingly low, or, when the lactometer read- ing, the specific gravity of the milk, the per cent, of solids not fat and the per cent, of fat are low. The specific gravity of the milk solids is normal in watered milk. Q. When is adulteration by both skimming and watering indicated? A. AVhen the_ lactometer reading and the specific gravity are ncirmal or slightly below and the per cent, of solids not fat is 1oa\'" and the per cent, of fat lower in proportion than the solids not fat. EXAMPLE. '11 A is the corrected lactometer reading, l.fi per cent, is the per cent, of butter fat in the above samples of milk. 27.4 is 85.6 per cent, of 32, which is the normal specific gravity of milk, or in other words the sample has l)een reduced 14.4. Hence, if this sample of milk had been adulterated with. water only, the per cent.. of butter fat would be reduced proportionately ; or, for example. S.5.6 per cent, of 3 = 2.56 per cent., which should be the per cent, of butter with the above per cent, of dilution. However, from the above it will be noticed that the butter fat, 1.6 per cent., has been reduced 53.3 per cent., hence the difi"erence between 85.5 and 53.3., or 32.3 per cent, of butter fat must have been skimmed off the milk, aside from being adulterated. TESTS FOR ACID IN MILK 55 DIVISION SIXTEEN. THE ACID TEST. Q. What causes milk to sour on standing for eighteen to twenty hours at a temperature of 60° to 70° F.? A. This change is brought abovit by bacteria converting the milk sugar of the milk into lactic acid. It generally takes about IS to 20 hours at 65° to 70° for them to grow in sufficient number to turn the milk sour enough so that it clabbers. Q. Why does milk clabber? A. Clabbering of milk is due to the formation of lactic acid, which causes the casein of the milk to coagulate. Q. Has lactic acid any value in milk from a commercial standpoint? A. It is chiefly responsible for the flavor of butter and cheese, but great care must be taken in their manufacture that a proper amount of this acid be developed. Q. If too much acid is developed how would it affect the butter? A. Butter would not have such a good keeping quality and would not have the proper flavor. Q. If the acid exists in milk in solution with other liquids, how can the amount be readily determined? A. By neutralizing the acid with alkalies. Q. What is meant by alkalies? A. An alkali is a substance that has chemical i)roperties directly opposite to an acid. Either of these is a powerful agent for disintegrating and corroding much of the organic and inorganic matter, but when the two are united they lose this power. Alkalies are such substances as lime, lye, soda, etc. However, for testing purposes they must be chemically pure. Hence, if lime is added to sour milk, the acid unites with the lime, forming a sulxstance which is neutral, neither alkaline nor acid. Q. Does a certain amount of alkali neutralize a certain amount of acid? A. Yes : if the per cent, of alkalinity of a solution is known, and the amount added to an acid sul^stance, the per cent, of acid in the solution can be calculated. Q. How can one tell when the alkali has neutralized the acid? A. By means of an indicator. This indicator is colorless in appearance if added to the acid, but turns pink when added to alkali, hence if a few drops of this indicator (which is commonly known as phenolphthalein) be added to the milk, the same will remain colorless until sufficient alkali has been added to neutralize the acid, and by adding a slight amount more the solution changes to a pink color. 56 TESTS FOR ACID IN MILK Q, How may you determine the acid by means of the Mann's test? A. Tlie Mann's test consists of a 50 cubic centimeter burette, a 5U cubic centimeter pipette, a white porcelain cup, a glass stirring" rod and a 1/10 normal solution of sodium hydroxide. This alkali can be bought in gallon bottles, and is made by dissolving four grams of sodium hydroxide, to which enough distilled water is added to make one liter of solution. Each cubic centimeter, containing .004 of a gram of sodium hydroxide, will neutralize .009 of a gram of lactic acid. This is obtained from the fact that a normal solution of lactic acid contains 90 grams of acid in each liter, or 1,000 cubic centimeters. A 10th normal solu- tion would then contain one-tenth as much, or 9 grams to each liter, and a cubic centimeter, which contains .001 as much as a liter, would contain .009 of a gram of lactic acid. With the ap- paratus and solution on hand, measure 50 cubic centimeters of cream with a pipette into a beaker. Rinse the pipette with dis- tilled water adding same to the beaker. Add five drops or more of indicator. Fill the burette to the zero mark with neutralizer, but before doing this be sure to see that the burette is absolutely free from water and acids. Probably the best way is to rinse the burette with a little of this solution. Now add the solution to the cream in a very slow manner until you notice that the solution ap- pears very reluctant in destroying the pinkish color on stirring. Then this neutralizing solution should be added drop by drop only. The moment the cream remains pink, the acid has been neutralized. The number of cubic centimeters of alkali added to the cream is read on the burette, and from this the percentage of acid is calcu- lated in the following manner : The number of cubic centimeters of alkali multiplied by .009, divided by the number of cubic centi- meters of cream, and multiplied by 100. Example. — It required 32 cubic centimeters of alkali to neu- tralize 50 cubic centimeters of cream ; what per cent, of acid is in the cream ? The formula would be like this: 33 X .009 X 100 = .576. 50 It is not essential to use 50 cubic centimeters of material. Any other amount may be used substituting the same for 50 in the above formula. When IT.fi cubic centimeters are used a result, accurate enough for all practical purpose's, may be obtained by dividing the cubic centimeters of alkali by '20. Suppose 4.4. cubic centimeters of alkali were used to neutralize 17.(5 cubic centimeters of milk or cream. Then 4.4 h- 20 = .32 per cent, of acid. Q. How may you determine the acid by means of the Far- rington alkaline tablet test? A. The Farrinoton alkaline tablet test works on the same TESTS FOR ACID IN MILK 57 principle as the Mann's test. Instead of the neutralizer being in a solution form, as in the Mann's test, it is put up in tablets. Dis- solve five tablets in enough water to make 97 cubic centimeters of solution. The tablets must be dissolved so that it becomes a per- fect solution. Measure out with a Babcock pipette 17.6 cubic cen- timeters of the milk or cream to be tested into a wihite porcelain cup (a white cup is preferable because one can more easily see the pink color). Add solution to milk or cream until a permanent pink color is obtained, the sarne as in the Mann's test. Read the num- ber of cubic centimeters solution used to change the color, and this will indicate the number of hundredths of one per cent, of acid in milk or cream. It is convenient to make up the Farrington solution in a 100 c.c. graduated cylinder fitted tightly with a stopper. Then the solution may be poured directly from the cylinder and the c.c. used, read from the cylinder graduation. Example. — If it requires 50 cubic centimeters of tablet solution to neutralize the acid of the cream, then the acidity would be .5 per cent. Q. How may acidity be estimated approximately by the Far- rington tablets? A. For some purposes it is advantageous to determine whether milk contains more or less than .2 per cent, of acid. The solution for this test is prepared by dissolving tablets at the rate of 2 to each ounce of water used. The test is made by mixing equal parts of the tablet solution and the milk to be tested in a white cup. If the milk remains white it contains more than .2 per cent, of acid while if it turns pink it contains less than .2 per cent, of acid. The deeper the pink color the sweeter the milk. Q. How may you obtain the per cent, of acidity by means of the Marschall test? A. In this acid test the neutralizer used is the regular stand- ard 1/10 normal alkali, which can be obtained from all dairy supply houses and experiment stations. The Marschall acid test contains the following parts : Combined burette and bottle for the neutralizer. 9 cubic centimeter pipette. Bottle of indicator. y2 gallon bottle of neutralizer. It is necessary only to fill the burrette bottle with neutralizer. place it on a small box or shelf at a convenient height, and the acid test is ready for use. After carefully mixing the milk or cream, fill the 9 cubic centi- meter pipette, empty it in the cup and add a couple of drops of the indicator. If heavy cream is tested, it is preferable to fill the pipette again with water, and add the rinsing water to the con- tents of the cup. Fill the graduated burette by tipping the bottle and place level again. Adjust the burette and rubber stopper so that the neutralizer will stand at the zero mark in the burette, then 58 TESTS FOR ACID IN MILK let the neutralizer run into the cup a little at a time, shaking the cup by circular motion, until the contents have attained a pink shade and do not turn white again within five or ten seconds. The number of cubic centimeters of the neutralizer used will then di- rectly show how much acid the milk or cream contained, giving it in 0.1 per cent. acid. If 2 cubic centimeters of neutralizer have been used, the milk contained two-tenths of one per cent., and if, for instance, a sample of cream takes 5.6 cubic centimeters of neu- tralizer, it contained 56 hundredths of 1 per cent, of acid, generally written as .3 per cent, acid and .56 per cent. acid. To facilitate the readings, the burette is graduated in 2/10 of one cubic centimeter only, but 1/10 cubic centimeter cart easily be read off when re- quired. As all tests start at the zero mark, there are no calcula- tions necessary to determine how much neutralizer has been used, with the resulting possible errors. Before starting the test, lift the rubber stopper in the neck on top of the bottle and replace securely. This operation releases the pressure in the bottle, and should be repeated each time the neu- tralizer does not run freely from the burette. The burette valve is a ball valve, and is worked by pressing the rubber tubing between the fingers. Q. Is there a more convenient way to test a great number of samples of milk? A. If many samples of milk are tested at the receiving plat- form with the Marschall test, it is convenient to get about 2 dozen 2 oz. bottles, with wide mouths, and into each put 2 cubic -centi- meters of neutralizer from the ])urette, and also 2 drops of in- dicator. The 9 cubic centimeters of the milk taken as sample is then simply added to one of the bottles and shaken. If the mixture does not turn white the milk contains less than .2 per cent. acid. This is generally taken as a standard. Q. What per cent, of acid will the acid test show in freshly drawn milk? A. About .07 per cent, due to acid phosphates, free carbonic acid gas and an acid reaction of the casein. Lactic acid develops after the milk is drawn. Q. What is the per cent, of acid in milk when it begins to taste sour? A. About .."O to .85. Q. What amount of acid is allowable in market milk? A. Retail milk should contain less than .2 per cent, of acid. Milk received at the factories should not contain more than .2 per cent, acid, and milk containing .25 per cent, acid and over can not be pasteurized. ^lost butter makers would refuse milk showing more than .2 per cent. acid. Q. Does a change in the per cent, of acidity change the flavor ? PRESERVATIVES o9 A. Yes ; the greater the amount of acid developed in cream the more sour it will taste. Q. What per cent, of acid should there be in cream for butter making? A. Cream ready to churn should contain .4 to .55 per cent, acid, according to whether mild or highly flavored butter is wanted, and also depending upon the per cent, of fat in the cream. The higher the per cent, of fat the less acid is needed. Q. What per cent, of acid should there be in starters used for butter and cheese making? A. Starter for butter or cheese should be used immediately, or else cooled down quickly, when it shows .7 to .85 per cent. acid. DIVISION SEVENTEEN. DETECTION OF PRESERVATIVES. Q. How may formalin be detected in milk? A. (a) To about 10 c.c. of milk in a test tube or in the Babcock test bottle, add an equal amount of well water. Pour concentrated sulphuric acid down the side of the tube, taking care not to mix with the milk. If formalin is present a distinct purple ring will form at the junction of the milk and acid. The purpose of the well water is to add iron. This may be supplied by adding 4 or 5 drops of a 10 per cent, solution of ferric chloride. It will not be neces- sary when commercial sulphuric acid is used. (b) A more delicate test is made as follows: Prepare a solu- tion of concentrated hydrochloric acid (sp. gr. 1.2 ) containing 2 c.c. of 10 per cent, ferric chloride ( Fe CI.,) per liter. To 10 c.c. of milk add 10 c.c. of this solution in a white dish. Bring slowly to the boiling point. If formalin is present a violet color appears. Q. How may carbonate of soda be detected in milk or cream? A. To 10 c.c. of milk in a test tube add 10 c.c. of alcohol and a few drops of a one per cent, solution of rosolic acid and mix.. If a carbonate is present a rose red color appears, while pure milk shows a yellowish red color. Q. How. may borax and boracic acid be detected in milk or cream? A. (a) A preliminary test for borax may be made by im- mersing a strip of tumeric paper in 100 c.c. of the suspected milk to which 7 c.c. of hydrochloric acid has been added. The tumeric paper will acquire a peculiar red color on drying. (b) The following method is a more delicate test: Pour 15 or 20 c.c. of milk into a porcelain dish, make it alkaline with sodium hydrate, evaporate and burn to an ash. Add a few drops of diluted hydrochloric acid to the ash. Soak a strip of tumeric paper in this solution and dry with heat. If borax or boracic acid is present, the paper will be a distinct cherry red when drv and turn olive ereen on the addition of dilute ammonia. 60 BACTERIA IN MILK DIVISION EIGHTEEN. BACTERIA IN MILK. Q. What are bacteria? A. The lowest form of plant life. They are single celled and microscopical. Q. How do bacteria reproduce? A. By fission or by one bacterium simply dividing into two. Q. What are spores? A. When some bacteria come under unfavorable conditions for growth they form spores. A small bright spot appears within the bacterium and gradually becomes larger. The old cell breaks up and disappears, leaving- the spore. This spore is very resistant to heat, drying and the various things which usually destroy bac- teria. A comparatively small number of different species of bac- teria are capable of forming spores. Q. What things are necessary to bacterial growth? A. Food, moisture, heat between certain limits and absence ■of light. Some species demand the presence of air, others the absence of air, while still others will grow either in its presence or absence. The common lactic acid bacteria which cause milk to sour belong to the last class. Q. What is the most favorable temperature for bacterial growth ? A. Most bacteria grow most rapidly between 80° and 100° F. Some will grow rapidly between 60° and 70°, the common lactic acid bacteria of milk being in this class. Most species are injured by a temperature above 100° but a few types will grow at 140° F. There is very little bacterial growth below 50° F. Q. How may bacteria be killed? A. The practical means are heat, direct sunlight and chemical disinfectants. Q. How much heat is necessary to kill bacteria? A. A temperature of 140° F. for one-half hour will kill most -growing bacteria. Higher temperatures will kill them more quickly. Bacterium tuberculosis is killed by 140° F. for 20 min- utes. A temperature of 160° F. for one minute or less will kill the germsof tuberculosis, diphtheria, typhoid and most disease pro- ducing germs. Q. How may bacterial spores be killed? A. By heating under 15 pounds steam pressure for 15 min- utes. This gives a temperature of about 240° F. Heating in a dry oven at a temperature of 300° F. for one-half to one hour will kill them. BACTERIA IN MILK 6t Q. What are some chemical disinfectants? A. A 5 per cent, solution of carbolic acid. A 1 per cent, solution of mercuric chloride. A 5 per cent, solution of formalin. Slaked lime. These are of value in stables and in any place where the milk will not come in direct contact with them. Q. What is pasteurization? A. Pasteurization is the application of sufficient heat to kill all growing- or vegetative bacteria and then cooling to a low tem- perature. Pasteurization does not kill spores. The most satis- factory way to pasteurize milk is to heat to 140° F. for 20 to 30 minutes. Q, What is sterilization? A. Sterilization is accomplished by the application of suf- ficient heat to kill all bacterial life. It is not practical to sterilize milk for market purposes. Heating under 15 pounds steam pres- sure for 15 minutes or steaming for one-half hour on three consecu- tive days will sterilize liquids. Glassware and tinware may be sterilized by heating under 15 pounds steam pressure for 15 min- utes. In laboratory work glassware is sterilized by heating to 150° C. or 300° F. for one hour in a hot air oven. Q. How should milk utensils be washed? A. They should first be rinsed in cool or luke-warm water, then washed in boiling water containing an alkali, such as carbon- ate of soda, sal soda or sodium borate. They should then be steamed or rinsed with wlater which has been heated above the boiling point for a least one hour. It is very desirable to sterlize under 15 pounds steam pressure when this is possible. Q. What are the sources of bacteria in milk? A. Dirt and dust from the cow, dust in the air. imperfectly sterilized utensils, impure water, the hands and clothing of persons, milking and handling the milk. Q. What are the sources of disease germs? A. The handling of milk by persons diseased or who have come in contact with diseased persons ; imperfectly sterilized milk bottles or other utensils returned from homes where contagious diseases exist; contaminated wash water; diseased cows. Q. What means may be employed to secure a low bacterial content of milk? A. Healthy cows ; healthy milkers ; clean milkers, both as to hands and to clothing; clean cows; clean stables ; brushing cows and cleaning stables long enough before milking to allow the dust to settle, handling hay and bedding after milking and not before ; wiping the cow's udder and flanks with a damp cloth before milk- ing; washing the udder with soap and water when badly soiled" 62 FERMENTATION TESTS using small top milk pails ; using clean sterilized utensils ; cooling milk below 50° F. as soon as milked and keeping it cool. Q. What are the effects of bacteria on milk? A. The most common effect is the souring of milk by the lactic acid bacteria which produce lactic acid from the milk sugar. Others produce gas which is troublesome to cheese makers. Still other effects are the production of sweet coagulation, the produc- tion of undesirable flavors, the production of ropy or slimy milk, the production of abnormal color. Q. Are all bacteria harmful to milk? A.. No. Some varieties are neutral or have no effect. The lactic acid are of great value to the butter maker, cheese maker and the maker of fermented milks. When lactic acid bacteria are de- veloping they tend to check the growth of undesirable species. Q. What is a starter and how made? A. A starter is a culture of lactic acid bacteria in milk. It may be made by letting clean milk sour naturally at a temperature of about 65° F. It may be made from a commercial or pure culture of lactic acid bacteria secured from various firms which prepare them. The starter may be made from the same by pasteurizing one quart of milk at 180° F. for 30 minutes and cooling to 65° F. Then add the pure culture and hold at 65° F. until curdled. This will not have the good flavor desired but may be used to inoculate a second culture prepared in the same manner. This and follow- ing cultures will have a clean acid flavor if proper care has \een used to prevent contamination. DIVISION NINETEEN. FERMENTATIOX TESTS. Q. What are fermentation tests of milk? A. Tests in which fermentation is allowed to take place in the milk or the curd to detect bad flavors, odors and gas produc- tion. They are of special value to cheese factories and milk dealers for testing out the milk of different patrons and to dairy- men for testing the milk of different cows. Q. How may the Gerber fermentation test be made? A. Secure samples of the milk to be tested in sterile bottle with stoppers or caps. Warm to from 98° to 104° F. and hold at that temperature until curdled, by placing in water bath. The length of time required to cUrdle. the odors developed and pres- ence or absence of gas holes in the curd will indicate the quality of the milk. Q. How may the curd test be made? A. Secure samples of the milk to be tested in sterilized wide mouth bottle fitted with a cover. At least one-half to two-thirds RENNET 63 of a pint of milk should be used for each test. Warm the milk to !)8° F. and add about 10 drops of rennet to each bottle. Mix by giving the bottle a rotary motion and let stand until curdled, which will be about 20 minutes. Cut the curd into small cubes, using a clean, sterile case knife. Stir occasionally for 30 to 45 minutes to keep the curd from matting and then pour off the whey. It will be removed more completely by pouring it off two or three times. Then set the bottles in water which should be kept at 98° F. for (3 to 12 hours. The quality of the different milks will be indicated by examining the dift'erent curds for odors and by cutting through them with a knife, noting the gas holes. Gas should not form in the curd of sweet milk. DIVISION TWENTY. REXXET. Q. What is rennet? A. An extract obtained from the fourth stomach of a young calf. It is supposed to contain enzymes, renrtin and pepsin. The former has a coagulating action on milk casein and the latter a digesting action. Q. For what is rennet used? A. For precipitating the casein of milk in cheese making. Q. Does the curd thus formed contain constituents other than casein? A. Yes. It contains water, the greater part of the butter fat ■ >f the milk, a small amount of milk sugar, albumen and ash. Q. What factors influence the action of rennet? A. It acts most satisfactorily for cheese making at 86° to ^^° F. Increase of temperature hastens and decrease of tempera- ture retards its action. Rennet extract is rendered inactive if ex- posed to a temperature of 140° F. for some time. Weak solutions are affected by a temperature as low as 105° F. Generally speak- ing the greater the acidity the more rapid the action of rennet on milk. It acts slowly if at all on pasteurized milk, because the soluble calcium salts have been precipitated. Q. What is the action of rennet in cheese ripening? A. The pepsin aids in breaking down the casein into more soluble compounds. DIVISION TWENTY-ONE. FEDERAL STAXDARDS FOR DAIRY PRODUCTS. The following are the standards for milk and its products as given in Circular Xo. 19, Standards of Purity for Food Products, U. S. Department of Agriculture : Milk is the fresh, clean, lacteal secretion obtained by the com- 64 FEDERAL STANDARDS plete milking of one or more healthy cows, properly fed and kept, excluding that obtained within fifteen days before and ten days after calving, and contains not less than eight and one-half (8.5) per cent, of solids not fat, and not less than three and one-quarter (3.35) per cent, of milk fat. Blended milk is milk modified in its composition so as to have a definite and stated percentage of one or more of its constituents. Skim-milk is milk from which a part or all of the cream has been removed and contains not less than nine and one-quarter (9.25) per cent, of milk solids. Pasteurized milk is milk that has been heated below boiling sufficiently to kill most of the active organisms present and im- mediately colled to 50° F. or lower. Sterilized milk is milk that has been heated to the temperature of boiling water, or higher for a length of time sufficient to kill all organisms present. Sweetened condensed milk is milk from which a considerable portion of the water has been evaporated and to which sugar (sucrose) has been added, and contains not less than twenty-eight (28) per cent, of milk solids, of which not less than twenty-seven and five-tenths (27.5) per cent, is milk fat. Unsweetened evaporated or condensed milk — The standard for unsweetened evaporated or condensed milk has been changed by Food Inspection Decision No. 131, to read as follows : "(1) It should be prepared by evaporating the fresh, pure, whole milk of healthy cows, obtained by complete milking and excluding all milkings within 15 days before calving and 7 days after calving, provided at the end of this 7-day period the animals are in a perfectly normal condition. (2) It should contain such percentages of total solids and of fat that the sum of the two shall be not less than 34.3 and the percentage of fat shall be not less than 7.8 per cent. This allow'S a small reduction in total solids with increasing richness of the milk in fat. (3) It should contain no added butter or butter oil incor- porated either with whole milk or skimmed milk or with the evaporated milk at any stage of manufacture." Condensed skim-milk is skim-milk from which a considerable portion of the water has been evaporated. Buttermilk is the product that remains when butter is re- moved from milk or cream in the process of churning. Goat's milk, ewe's milk, etc., are the fresh, clean, lacteal secre- tions, free from colostrum, obtained by the complete milking of healthy animals, other than cows, properly fed and kept, and con- FEDERAL STANDARDS 65 form in name to the species of animal from which thev are obtained. Cream is that portion of milk, rich in milk fat, which rises to the surface of milk on standing, or is separated from it by centrif- ugal force, is fresh and clean and contains not less than eighteen (18) per cent, of filk fat. Evaporated cream, clotted cream, is cream from which a con- siderable portion of water has been evaporated. Milk-fat, butter fat, is the fat of milk and has a Reichert-Meis- sel Xumber not less than twenty-four (24) and a specific gracity (40° C.) not less than CDOo ( j (40° C.) *'Butter is the clean, non-rancid product made by gathering in any manner the fat of fresh or ripened milk or cream into a mass, which also contains a small portion of the other milk constituents, with or without salt, and contains not less than eighty-two and five-tenths (82.5) per cent, of milk fat. By acts of Congress ap- proved August 2. 1886, and May 9, 1902, butter may also contain added coloring matter. Renovated butter, process butter, is the product made by melt- ing butter and reworking, witliout the addition or use of chemicals, or any substance except milk, cream, or salt, and contains not more than sixteen (l(i) per cent, of water and at least eighty-two and five-tenths (82.5) per cent, of milk fat. Cheese is the sound, solid and ripened product made from milk or cream by coagulating the casein thereof with rennet or lactic acid, with or without the addition of ripening ferments and seas«^n- ing. and contains, in the water-free substance, not less than fifty (50) per cent, of milk fat. By act of Congress, approved June (>. 190(i, cheese may also contain added coloring matter. Skim-milk cheese is the sound, solid and ripened product made from skim-milk by coagulating the casein thereof with rennet or lactic acid, with or without the addition of ripening ferments or -reasoning. Gaot's milk cheese, ewe's milk cheese, etc., are the sound, rip- ened products made from the milks of the animals specified, by coagulating the casein thereof with rennet or lactic acid, with or without the addition of ripening ferments and seasoning. Ice cream' is a frozen product made from cream and sugar, with or without a natural flavoring, and contains not less than fourteen (14) per cent, of milk fat. *The inspection of butter and renovated butter is done by the Internal Revenue Department. All butter containing Ki per cent. of moisture or more is classed as adulterated butter by the Internal Revenue law. If it is otherwise entitled to the name, it will pass inspection if it contains less than 16 per cent, of moisture. 66 FEDERAL STANDARDS Fruit ice cream is a frozen product made from cream, sugar, and sound, clean, mature fruits, and contains not less than twelve (12) per cent, of milk fat. Nut ice cream is a frozen product made from cream, sugar and sound, non-rancid nuts, and contains not less than twelve (12) per cent, of milk fat. Whey is the product remaining after the removal of fat and casein from milk in the process of cheese-making. Kumiss is the product made by the alcoholic fermentation o* mare's milk or cow's milk. Q. What departments of the Federal Government are re- sponsible for the enforcing of the above regulations? A. The United States Department of Agriculture enforces all of the regulations except those relating to butter and renovated butter. The inspection of butter and renovated butter is done by the Internal Revenue Office of the Treasury Department. Q. What is the jurisdiction of each? A. The Department of Agriculture enforces its regulations only when products are placed in interstate commerce, i. e., ship- ped from one state to another. Products remaining within a state are subject only to the requirements of the state. The Internal Revenue Office has jurisdiction wherever and whenever the butter is found. NOTES 67 DIVISION TWENTY TWO. LABORATORY EXERCISES. GENERAL DIRECTIONS. 1. Each student must be supplied with a dairy outfit. The key for the locker containing the same may be secured from the chemical store room after the laboratory deposit has been made and assignment received from the instructor in charge. 2. Each student must be supplied with a white coat and white apron for laboratory work. 3. Each student must clean his desk and all apparatus used by him before leaving the laboratory. 4. The breakage or loss of any glassware or other apparatus placed in the laboratory for general use will be charged to the class as a whole unless replaced by the student responsible. For references read : Farrington and Woll's "Testing Milk and its Products ;" Van Slyke's "Modern Methods of Testing Milk and Milk Products." EXERCISE I. Check all glassware and report at once any missing or broken ]jieces. Wash all glassware in hot water, using Wyandotte wash- ing powder. A good solution for occasional use in cleansing glassware is made by dissolving 1 pound of potassium bichromate in 1 gallon of sulphuric acid. This may be diluted with water or used full strength. A good way to use these materials in cleansing test bottles is by dissolving a small amount of potassium bichromate in hot water in a becker. Place a small amount of this solution in test battle and add sulphuric acid. 68 LABORATORY EXERCISES EXERCISE II. CALIBRATION. For methods see Division 7. (a) Calibrate all- 10% whole milk bottles witli the plunger or Trowbridge calibrator. (b) Calibrate all