i Dy DAIRY FUNDAMENTALS BY OSCAR ERF PROFESSOR OF DAIRYING OHIO STATE UNIVERSITY OQ. GC. CUNNINGHAM ASSISTANT PROFESSOR OF DAIRYING OHIO STATE UNIVERSITY Published by the Authors COLUMBUS, OHIO 191 Copyright, 1911 by OSCAR ERF and O. C. CUNNINGHAM “ pee Sc1.A300469 Division. E The TH. LV. NG WE: VEL; Wore: IX. x, ae Soll: wae SEN: poe XVI. XVII. XVIII. XIX. xX. > @.G8 TABLE OF CONTENTS. Page ILLITE wast vce aoe he 47 erection or Adulteration im Malka. sc, dake an 48 fade cicm bests for Milie-andsCreatm-... «> ssn ¢ eee: 51 DIEKCEMONROUnE GOSEIVALEVOSe a 20.0 cleans sae pits Saleen 55 PEA GUA WA Fa 2d co Wo ee a Sa re oe 8, 0 aacbe tc oie eter ame 55 RE GiNGHPA LONE GSES Say tne Oo a dvien Wes Statues ae alas sity abe 58 He NCU ercoe ayes, Midge cote cups nee ep aephiacra gees aeyae cee 59 Federal otandards, con sDairy “Products: 2)... .aacteon =. 59 Pa bALOny inp EPCIS Ei Go cre h 3S oie ti ose eter a ae 62 he me we ae Fe ne 8 DAIRY FUNDAMENTALS DIVISION ONE. MILK AND BUTTER FAT. Question. What is milk? Answer. Milk is the special fluid secreted by the females of milk giving animals (the Class Mammalia )for the purpose of nourishing the young until they are capable of seeking for them- selves the kind of food which they can easily digest. Of what is milk composed? Of water and milk solids. Is water in milk any different from distilled water? No. What are the milk solids? The milk solids are fat, milk sugar, albuminoids, and ash. What is milk serum? Milk serum is the water and all of the solids except the fat. What is milk fat or butter fat? It is a mixture of a number of distinct fats found in milk and is re chief constituent of butter. Q. Of what are these fats composed? A. Fatty acids and glycerine. Q. What are the different milk fats and the per cent. of each in butter fat? POFOrOPrPOord A. BAUeyriit Bk eee es 3.85% Molatile\Caproiny. <4. .40. nae. ae 3.60% Capry linus a oad OO Ve Olen hes eee eae: 35.00% PaAlmatitie: sah eve ce ost 0 70 Non Volatiles Myristin. 0 s.< ce ase 20.20% Pattie oe at es 7.40% Capri sy Mpa vac oe eee 1.90% StEAMINE nied ee oe 1.80% 100.00% Q. What is a volatile fat? A. O>O A. The Babcock tester is as essential in buying milk or cream as the scale is in buying corn. Q. Name the pieces of apparatus which are used in the Bab- cock test. A. (1) Centrifuge (or whirling machine), (2) graduated Bab- cock milk test bottle, (3) pipette, (4) acid measure and (5) dividers. Q. Are there any chemicals used in making the test? A. Yes; one—commercial sulphuric acid. 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). 2. See that the test bottles and pipette are clean. 3. See that the centrifuge is properly oiled and in order before starting. 4. See that the sample of milk to be tested is thoroughly mixed. (If a composite sample follow the details as explained below.) 5. See that the temperature of the sample of milk is not below 50sseeenor above. 70°F. 6. Measure out 17.6 cubic centimeters of the milk with the pipette and put it into the test bottle. TESTING MILK 19 7. See that the sulphuric acid is of the proper strength (sp. gr. 1.82 to 1.83). 8. Measure out 17.5 cc of sulphuric acid and pour into the test bottle with the milk. 9. 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 5 minutes at the proper speed, then add hot water to the mixture until it reaches the base of the grad- uated neck. iP it into centrifuge and rotate the bottle two minutes more. 13. Fill with hot water to 7 per cent. or 8 per cent. mark. 14. Whirl 1 minute. 15. Remove bottles to hot water ae with water at a tem- perature of 140° F. and deep enough to cover fat column. Q. How are milk test bottles graduated? A. They are graduated from 0 to 10 per cent._ Each one per cent. is numbered and each one per cent. space is divided into five parts, each representing .2 of one per cent. Q. What is the basis for the graduation of test bottles? In calculating what quantity of butter fat could be con- veniently read with the greatest accuracy and with the smallest cost, Doctor Babcock estimated that a space in a narrow glass tube holding two grams of water and representing 10 per cent. of a quan- tity of milk would best meet these conditions. Accordingly, a tube containing such a column of water was marked at the base and top of the column, and this space was divided into ten equal portions, representing per cents. Each division was then divided into five parts, each representing two-tenths of one per cent. Since this column of water weighs two grams, an equal volume of butter fat would weigh 1.8 grams (fat having a specific gravity of approxi- mately .9). Then 1.8 grams represents 10 per cent. of a certain volume which must be 18 grams. Hence 18 grams of milk is the proper amount to use in testing for butter fat with the Babcock Bester. Q. Why are 17.6cc of milk used? On account of the inconvenience of weighing, these weights have been reduced to their equivalent volumes. Considering the average specific gravity of milk as 1.032, the equivalent volume of 18 grams of milk is found to be nearly 17.44 cubic centimeters; e.g, 18 = 1.032 = 17.44. Allowing for the small quantity that ad- heres to ie side of the pipette, 17.6 cubic centimeters has been taken as the proper amount to be measured out. Q. Is the graduation of testing apparatus always correct? me, NO: 20 TESTING MILK Q. How is the accuracy of graduation determined? A. By calibration or measuring with water, mercury or a plunger. Q. How are milk test bottles calibrated with water? A. See that the bottle is cleaned thoroughly. Fill the bottle to the zero mark with distilled water. Remove any surplus water from inside of neck of bottle with a strip of blotting or filter paper. Measure into the bottle Icc of distilled water from an accurately marked burette or pipette. This should fill to the 5 per cent. mark. One more cc of water should fill to the 10 per cent. mark. Each 2cc equals one per cent. on neck of bottle. Instead of measuring the water, the bottle filled to the zero mark may be balanced on a delicate scale. Then it should take just one gram of distilled water to fill to the 5 per cent. mark and 2 grams to fill to the 10 per cent. mark. Each .2 gram equals 1 per cent. on neck of bottle. Q. How may test bottles be calibrated by use of mercury? A. See that the bottle is thoroughly cleaned and dry—espe- cially free from fat. The space in the Babcock test bottle between the zero and the ten-per-cent. mark holds just two cubic centi- meters. Pour two cubic centimeters of mercury (by weight 27.18 grams) into the test bottle. Insert a smooth cork into the bottle until the end reaches the ten-per-cent. mark. Invert the bottle. If it is correctly graduated, the mercury wiil just reach the zero mark. Q. How may 10 per cent. bottles be calibrated by a plunger? A. This tester consists of nothing more than a piece of metal of such a size that it will displace exactly two cubic centimeters of liquid. It is divided into two parts, connected with a thin wire, and each part displaces one cubic centimeter, which is equal to 5 per cent. on the graduated scale of the test bottle or the two parts are equal to 10 per cent. It is used as follows: Fill the bottle with milk, alcohol or water so that its highest point is exactly even with the 0 mark. Slowly lower the tester into the bottle until the liquid rises about half way between the two sections. At that point should be the five-per-cent. mark. That point having been established, slowly lower the entire tester into the bottle so that the liquid rises over the top of the upper section about one-eighth of an inch, and if the liquid is ex- actly even with the ten-per-cent. mark, and was the same at the five-per-cent. mark, the bottle is correct. Before using again, the liquid adhering to the tester should be wiped .off. See that the neck is practically free from adhering drops of liquid and that no air bubbles are located between the tester and the neck of the bottle. Bottles of more than one-tenth of one per cent. out of the way may be considered unfit for use. TESTING MILK 21 Q. How may 8 per cent. milk bottles be calibrated? A. Most conveniently by distilled water, remembering that each .2cc or .2 gram equals 1 per cent. on neck of bottle. Q. How may pipettes be calibrated? A. 588.23 = 1588.23 pounds of milk containing 3.5 per cent. fat. Q. How much milk containing 5.5 per cent. butter fat and how much skim-milk containing one-tenth of one per cent. butter fat will be needed to produce 1000 pounds of milk containing 3.5 per cent. butter fat? A. (See parallelogram above.) 3419-54 5.4 : 3.4 :: 1000 :x,.629.6 pounds of milk containing 5.5 per cent. butter tat. 1000 — 629.6 = 370.4 pounds of skim-milk containing one- tenth of one per cent. butter fat, or 5.4 :2 :: 1000 :x = 370.4 pounds of skim-milk containing one- tenth of one per cent. butter fat. Q. How much skim-milk must be removed from 780 pounds of milk testing 3 per cent. butter fat to increase the test to 4 per cent.? A. 3 |_——______| 3.9 pounds of milk containing 3 per cent. butter fat to use. |1 pounds of skim-milk to remove from 3.9 pounds of milk contain- ing 3 per cent. 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. 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. butter fat 1 pound of skim-milk must be removed to increase the per cent. of fat to 4. Therefore, 3.9 :1 :: 780 :x = 200 pounds of skim-milk to remove, or 1X 780 = 200 pounds of skim-milk to remove. 3.9 780 — 200 = 580 pounds of milk containing 4 per cent. but- ter fat. Q. How much milk containing 3 per cent. butter fat will be required to produce 780 pounds of milk containing 4 per cent. but- ter fat? A. (See the diagram above.) The 780 pounds of milk containing 4 per cent. butter fat will be the number of pounds of milk containing 3 per cent. butter fat less the number of pounds of skim-milk removed. Since 3.9 repre- sents the amount of milk to use and 1 the skim-milk removed, ee Se BUTTER-FAT EQUIVALENT 47 3.9 — 1 or 2.9 will represent the 780 pounds of milk containing 4 per cent. butter fat. Therefore, we have the proportion ‘ %.9 :3.9 :: 780 :x = 1048.96 pounds of milk containing 3 per cent. butter fat to make 780 pounds of milk containing 4 per cent. butter fat; or : 3.9 7380 = 1048.96 pounds of milk containing 3 per cent. but- 2.9 ter fat to make 780 pounds of milk con- taining 4 per cent. of butter fat. DIVISION THIRTEEN. RULES. FOR CALCULATING BUTTER-FAT EQUIVALENT DPOUshPERENT PRODUCTS. Q. How can the price per gallon of cream equivalent to the price of butter fat be found? A. Multiply 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: What is the price per pound of butter fat if cream containing 20 per cent. fat sells for 50 cents per gallon? A gallon of 20 per cent. cream weighs approximately 8.4 pounds. 8.4 & .20 = 1.68 the pounds of butter fat in one gallon which is worth 50 cents. $.50 + 1.68 = $.297, 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 price per pound of butter fat you desire, the product will be the price per gallon for cream. To illustrate: At 32 cents per pound of fat what would be the price per gallon of cream containing 27 per cent. butter fat? 8.3 X .27 = 2.241 pounds of fat in 1 gallon. ede ee lente or 72 cents. the price of the 27 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. butter fat is worth 60 cents per gallon what is cream worth containing 25 per cent. butter fat? Ooms DO =. Xx HOS - 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 Pe DETECTION OF ADULTERATION 49 obtained the per cent. of fat and the lactometer reading, the per oe a not fat may be calculated by the following formula: 6 = per cent of solids not fat. L. Lactometer reading at 60°. F. Per cent. of fat. While the above formula is most convenient and is satisfactory for all practical purposes a more accurate formula is as follows: ---+ .2F = per cent. of solids not fat. 4 L. Lactometer reading at 60°. De 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. . 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 9% per.cent., and where it is not possible to get a sample of the pure milk for test- ing, use 8.5 as a standard for the first half of the season and grad- ually 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: 30.0 = — 15 per cent. solids not fat; then + aD x LOO 750 —— — ——_ = 83.3 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 specific 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? 50 DETECTION OF ADULTERATION A. When the specific gravity of the milk solids is above 1.34, skimming is to be suspected and when it is above 1.40 it is con- clusive. Q. How may the specific gravity of milk solids be determined? A. By the following formula: t S22 100s — 100 t ee, 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 solids of a milk were found to be 13 per cent. and the specific grav- ity of the milk 1.032. Then, (100 1.032) — 100 BE ue eo BOA A) a3 FOI) = OreOOR 1.032 13 —— = 1.31, the specific gravity of the milk solids. 9.899 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 spe- cific 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. When 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 in- dicated? A. When the lactometer reading and the specific gravity are normal or slightly below and the per cent. of solids not fat is low and the per cent. of fat lower in proportion than the solids not fat. EXAMPLE. 27.4 is the corrected lactometer reading. 1.6 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 been 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, 85.6 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 difference between 85.5 and 53.3, TESTS FOR ACID IN MILK 51 or 32.3 per cent. of butter fat must have been skimmed off the mill, aside from being adulterated. DIVISION FIFTEEN. tee ClD. TEST. Q. What causes milk to sour on standing for eighteen to twenty hours at a temperature of 60° to 70° F? ieee chis change is brought about by bacteria converting the milk sugar of the milk into lactic acid. It generally takes about 18 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 its chemical properties 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 substance 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 substance, 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 52 TESTS FOR ACID IN MILK the acid, and by adding a slight amount more the solution changes to a pink color. Q. How do you determine the acid by means of the Mann’s test? A. The Mann’s test consists of a 50 cubic centimeter burette, a 50 cubic centimeter pipette, a white porcelain cup, and a glass stirring rod. 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 and 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 ig 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 lke this: oe e009 S100 Fab: 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 17.6 cubic centimeters are used a result, accurate enough for all practical purposes may be obtained by dividing the cubic centimeters of alkali by .2. Suppose 4.4 cubic centimeters of alkali were used to neutralize 17.6 cubic centimeters of milk or cream. Then 4.4 + .2 = .22 per cent. of acid. Q. How do you determine the acid by means of the Farring- ton Alkaline Tablet test? MEST Ss2OR ACID: IN- MILK 53 _A. The Farrington Alkaline Tablet test works on the same 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 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 white 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 same as in the Mann’s test. Read the number of cubic centimeters solution used to change the color, and this will indicate the number of hundredths of one per cent. of acidity 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 solu- tion may be poured directly from the cylinder and the c.c. used, read from the cylinder graduation. Example.—lf 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 can you obtain the per cent. of acidity by means of the Marschall test? A. In this acid test the neutralizer used is the regular standard 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. 4 gallon bottle of neutralizer. _ It is necessary only to fill the burette 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 centt- 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 54 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 has attained a pink shade ‘and does not turn white again within five to 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 .2 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 can easily be read off when re- quired. As all tests start at the zero mark, there are no calculations 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 neutral- izer 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 a couple dozen 2 oz. bottles, with wide mouths, and in each fill 2 cubic centimeters of neutralizer from the burette, and also a couple of 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. f Q. What is the per cent. of acid in milk when it begins to taste sour? A. About DUMtTONL OO: Q. What amount of acid is allowable in market milk? . A. Retail milk should contain less than .2 per cent. of acid. Milk reecived 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. Most 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? A. Yes; the greater the amount of acid developed in cream the more sour it will taste. 22s PRESERVATIVES 55 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 SIXTEEN. DE LBCIION OF PRESERVATIVES. Q. How may formalin be detected in milk? ieee Lovapout 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 cl 3) 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 bi-carbonaté 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. Ifa 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. 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 dry and turn olive green on the addition of dilute ammonia. DIVISION SEVENTEEN. 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? 56 BACTERIA IN MILK 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, and heat between certain limits. Some species demand the presence of air, others the absence of air, while still others will grow either in its presence or absence. The com- mon 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 erowing bacteria. Higher temperatures will kill them more quick- ly. Bacterium tuberculosis is killed by 140° F. for 20 minutes. A temperature of 160° F. for one minute or less will kill the germs of tuberculosis, diphtheria, typhoid and most disease producing germs. Q. How may bacterial spores be killed? A. By heating under 15 pounds steam pressure for 15 minutes. 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. Q. What are some chemical disinfectants? A. A 5 per cent. solution of carbolie 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- janice BACTERIA IN MILK 57 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 bicarbon- ate of soda, sal soda or sodium borate. They should then be steamed or rinsed with water which has been heated above the boiling point for at least one hour. It is very desirable to sterilize 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 or bacteria? 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 ; 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 FERMENTATION TESTS or io) maker of fermented milks. When lactic acid bacteria are develop- ing 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 following cultures will have a clean acid flavor if proper care has been used to prevent contamination. DIVISION EIGHTEEN. FERMENTATION 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 production. They are of special value to cheese factories and milk dealers for testing out the milk of different patrons and to dairymen for test- ing 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 presence 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 bottles fitted with a cover. At least one-half to two-thirds of a pint of milk should be used for each test. Warm the milk to 98° 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 6 to 12 hours. The quality of the different milks will be indicated by examining the different 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. ‘a 37a RENNET 59 DIVISION NINETEEN. RENNET. Q. What is rennet? A. An extract obtained from the fourth stomach of a young calf. It is supposed to contain enzymes, rennin 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 of 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 87° I. 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 acid 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. FEDERAL STANDARDS FOR DAIRY PRODUCTS. The following are the standards for milk and its products as given in Circular No. 19, Standards of Purity for Food Products, U. S. Department of Agriculture. Milk is the fresh, clean, lacteal secretion obtained by the com- 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 (3.25) 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 cooled to 50° F. or lower. Sterilized milk is milk that has been heated to the temperature 60 FEDERAL STANDARDS of boiling water, or higher for a length of time sufficient to kill all organisms present. Condensed milk, evaporated milk, is milk from which a con- siderable portion of water has been evaporated 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. 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. 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- form in name to the species of animal from which they 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 milk 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 Number not less than twenty-four (24) and a specific gravity (40° C.) not less: thann0).905.(— ===) Gores) *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- or any substance except milk, cream, or salt, and contains not more ing butter and reworking, without the addition or use of chemicals than sixteen (16) per cent. of water and at least eighty-two and five-tenths (82.5) per cent. of milk fat. *The inspection of butter and renovated butter is done by the Internal Revenue Department. All butter containing 16 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. FEDERAL STANDARDS 61 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 season- ing, and contains, in the water-free substance, not less than fifty fa0) percent. of ‘milk fat. By act of Congress, approved June 6, 1906, 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 seasoning. Goat’ 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. 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 of mare’s milk or cow’s milk. The standard for unsweetened evaporated or condensed milk as given on page 60 has recently been changed by Food Inspection Decision No. 1381, as follows: ““(1) It should be prepared by evaporating the fresh, pure, whole milk of healthy cows, obtained by complete milking and exclud- ing 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 per- centage of fat shall be not less than 7.8 per cent. This allows 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.’ 62 NOTES DIVISION TWENTY-ONE. 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. ®. Each student must be supplied with a white suit 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 pieces. 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. NOTES EXERCISE II. CAEIB RATION. For methods see Division 7. (a) Calibrate all whole milk bottles with the plunger or Trowbridge Calibrator. (b) Calibrate skim-milk bottles by the use of mercury. (c) Calibrate cream bottles and pipettes by the use of burette and distilled water. , Report all inaccurate pieces to instructor in charge. Record all pieces calibrated and results. 64 LABORATORY EXERCISES EXERCISE III. TESTING WHOLE MILK. For method see Division 7. (a) Test a sample of milk in duplicate (using two bottles). (b) Test another sample of whole milk in duplicate. In each case read the fat column immediately on taking from centrifuge. Then place in water at temperature of 140° for 4 min- utes and read again. Let the bottles stand at room temperature and take readings every ten minutes until the fat solidifies. Record the test of each bottle at the three different readings. If the per cent. in duplicate bottles when read from the hot water bath varies more than .2 per cent. test must be made again. This rule will hold in all Babcock tests for milk. What is the color of the fat column and other contents of the bottle? Record any other facts noted. Problems.—How many pounds of butter fat in 475 pounds of the milk tested in (a)? How many pounds of butter fat in 360 gallons of the milk test- eduin(a)e Solve the same problems for the milk tested in (b). 66 LABORATORY EXERCISES EXERCISE IV. EFFECT OF DIFFERENT AMOUNTS OF ACID AND DIFFERENT TEMPERATURES ON THE BABCOGCK. TESi- Make 7 duplicate tests of a sample of whole milk as follows: (a) Use the regular amount of acid. (b) Use one-half the usual amount of acid. (c) Fill the bowl nearly to base of neck with acid. . (d) Warm both milk and acid to 110° F. before mixing. Use the usual amount of acid. (e) Cool both milk and acid to 40° F. before testing. (f) Test milk as usual but use chemically pure acid instead of the commercial. (g) Very carefully add 2 or 3 cubic centimeters of water to 17.5 c.c. of commercial acid. Use 17.5 c.c. of this mixture in mak- ing one test. Record the per cent. of fat in each bottle, the color of the fat column in each case and any other differences you may note. 68 LABORATORY EXERCISES EXERCISE V. COMPARISON OF STEAM AND HAND TESTERS AND DIFFERENT SPEEDS OF TESTER. (a) Test a sample of whole milk in duplicate in power tester. (b) Test same milk in duplicate in hand tester. (c) Test same milk in duplicate running at one-half usual speed. (d) Test in duplicate a sample of skim-milk. Record the test of each bottle and note any differences between tests in hand and power testers and at different speeds. 70 LABORATORY EXERCISES EXERCISE VI. SKIM-MILK AND CREAM TESTING. For methods see Divisions 8 and 9. (a) Test a sample of skim-milk, using two whole milk and two skim-milk bottles. Note and record results from both kinds of bottles. (b) Test a sample of cream in duplicate using 9 grams in 9-gram bottles. (c) Test the same cream in duplicate, using 9 grams of. cream in 18-gram bottles. What must be done to the fat reading when using 9 grams of cream in an 18-gram bottle? Use glymol in reading cream tests. Record results in full in regard to per cent. of fat, color of fat column, etc. Problems.—(a) How many pounds of butter fat in 650 pounds of the above cream? (b) How many pounds of butter fat in 300 gallons of the above cream? (c) How many pounds of butter fat were lost in 600 pounds of the above skim-milk? =1 nw LABORATORY EXERCISES EXERCISE VII. CREAM TESTING. (a) Test a sample of cream in duplicate in 9-gram 50 per cent. bottles. (1) Read the per cent. of fat directly after the tester has stopped. (2) Place in hot water at a temperature of 140° F. for 4 minutes and read again, placing back into the water. (3) Add glymol to top of fat column and read again. (b) Test the same cream, using 18 grams in an 18-gram cream bottle. Follow out (1), (2), (8) as above. (c) Test a sample of buttermilk in duplicate using skim- milk bottles. Record results in detail. Show the number of pounds of butter fat a creamery would pay for in buying 464 pounds of cream by the different readings of per cent. of fat in the above experiment. 74 LABORATORY EXERCISES EXERCISE VIII. TESTING CREAM, BUTTERMILK AND SKIM-MILK. (a) Take a sample of cream fom a cream can and test it for butter fat. What precautions are necessary to get a fair sample of cream from the can? See Division 9. How much butter can be made from 100 gallons of this cream if the overrun is 18 per cent.? (b) Test a sample of buttermilk for butter fat using 2 whole milk and 2 skim-milk bottles. How much butter fat did the butter maker lose in 840 pounds of this buttermilk? (c) Test a sample of skim-milk in 2 skim-milk and 2 whole milk bottles. What was the loss of butter fat in 940 pounds of this skim- milk? ° “ ies ci ME as 3 at 76 LABORATORY EXERCISES EXERCISE IX. TESTING BUTTER: For methods see Division 10. (a) Prepare a sample of butter for testing. (b) Test for butter fat using two cream bottles and one spe- cial butter test bottle. (c) Make 8 tests of the same butter for moisture by the Irish method. (d) Test the same butter for salt, making 3 titrations of the salt solution. (e) If your tests are correct what is the per cent. of consti- tuents other than salt, water and butter fat in this butter? How near to the legal limits are the per cents. of water and butter fat? 78 LABORATORY EXERCISES EXERCISE X. TESTING CHEESE: For methods see Division 10. (a) Secure a sample of several different kinds of cheese. Take three small pieces of éach and put into as many test tubes. Then add a few c.c. of water to one of each kind, a few c.c. of sulphuric acid to one of each kind, a few c.c. of hydrochloric acid to one of each kind. Note the effect of the different solvents on the different kinds of cheese during the class period and set away until the next period and examine again. (b) Test a sample of cheese for moisture. (c) Test the same cheese in duplicate for butter fat. (d) Test a sample of whey for butter fat, using 2 whole milk and two skim-milk bottles. (e) How much butter fat was lost in 560 pounds of this whey? 80 LABORATORY EXERCISES EXERCISE XI. TESTING CONDENSED MILK AND ICE CREAM FOR BUMTERS PAL: For methods see Division 11. (a) Test a sample of ice cream in duplicate. (b) Test one bottle of ice cream in same manner as ordinary cream and compare results with (a). Why does (b) not give good results? (c) Test a sample of unsweetened condensed milk in dupli- cate. (d) Test a sample of sweetened condensed milk in dupli- cate. LABORATORY EXERCISES 81 EXERCISE XII. ACIDELY. TESTS: For methods see Division 14. (a) Test a sample of sweet milk for acid by both Mann’s and Marschall’s tests, making two determinations by each method. (b) Repeat (a) with sour milk. (c) Repeat (a) with sweet cream. Be sure to rinse the pipette with distilled water when testing cream, running the rinsings into cup with the cream. (d) Repeat (a) with sour cream. (e) Repeat (a) with buttermilk. (f) Repeat (a) with some milk soured by Bacillus Bul- garicus. LABORATORY EXERCISES 83 EXERCISE XIII. foe USE OF THE’ LACTOMETER: For methods see Division 13. (a) Make the following determinations with a sample of milk and in the order given: (1) Per cent. of fat. (2) Lactometer read- ing. (3) Temperature of milk. (4) Lactometer reading corrected to 60° temperature. (5) Specific gravity of the milk. (6) Per cent. of solids not fat. (7) Per cent. of total solids. (8) Specific gravity of the total solids. (b) Add 10 per cent. of water to the above milk and again make the same determinations. ‘ vy 7 sand Ls dy ics Y LABORATORY EXERCISES 85 EXERCISE XIV. PELE CTION OF ADULTERATION! Test four different samples of milk in same manner as in Ex- ercise XIII. Determine which samples are adulterated and in what manner See Division 13. ie ae) y ZO, waned Neo FS Diatet wie be LABORATORY EXERCISES 87 EXERCISE XV. BART CASEIN TEST AND FERMENTATION’TESTS, For methods see Divisions 10 and 17. (a) Test in duplicate a sample of whole milk for butter fat. (b) Test the same milk for casein by the Hart Casein Test. (c) At the beginning of laboratory period sterilize two pint bottles for fermentation tests, by putting them in autoclave under 15 pounds steam pressure for 15 minutes. When bottles have cooled prepare sample of milk for Gerber fermentation test in one and for curd test in the other. Examine on the two following days for odors and gas production. (d) How much cheese per hundred pounds may be made from the milk tested in (a) and (b)? Use both formulas given. LABORATORY EXERCISES 89 EXERCISE XVI. PRESERVATIVES. For methods see Division 15. (a) Test each of the samples of milk provided for formalde- hyde, borax or boracic acid, and sodium carbonate. 90 LABORATORY EXERCISES EXERCISE XVII DETECTION OF OLEOMARGARINE AND RENOVATED BULTER:. For methods see Division 10. (a) Examine the samples of material furnished and determine which are butter, which are oleo and which renovated butter. (b) Test one sample of each product for moisture, by one of the tests given for determining moisture in butter. LABORATORY EXERCISES 91 EXERCISE XVIII COMPOSITE TESTS. See composite tests under Division 7. (a) Test for butter fat each of 9 samples furnished. Divide the 9 samples into three groups of three each. Take three com- posite samples, one from each of the three groups at the rate of 1c. c. for each pound of milk represented by the different samples. The pounds of milk will be noted on the label of each sample. Place a corrosive sublimate preservative tablet in each com- posite sample, shake until dissolved, stopper tightly and set aside until next period for testing. (b) Determine the number of pounds of fat in the milk repre- sented by each of the above samples. Determine the average per cent. of fat in the 9 samples and the average per cent. in each of the groups. Compare these averages with the tests of the com- posites at the next period. (c) Beside the composite samples tightly stopper two other samples and set away without preservative until the next testing period. Record the tests of these samples to be compared with their tests at the next period. ts +n Prades LABORATORY EXERCISES 93 EXERCISE XIX. TESTING COMPOSITE SAMPLES AND CREAM. (a) Test the three composite samples saved from last period and compare tests With average of the individual tests. (b) In taking these composite samples, why was it necessary to take them proportionately, or 1 c.c. for each pound instead of an equal amount, such as 15 c.c. from each sample? (c) Test the two samples held over from last period witheut preservative. ' If they are curdled, test as recommended for curdled milk in Division 7, and compare per cent. of fat with that obtained in former tests. (d) Test a sample of cream for butter fat in duplicate. 94 LABORATORY EXERCISES EXERCISE XX. EXPERIMENTS WIPRe RENNET. Note Division 18. Dilute some rennet by putting 5 c.c. of rennet into a 50 c.c. glass flask and filling the flask to the mark with water. (a) Warm some sweet milk to 86° F. Add two 17.6 c.c. pi- pettefuls to a beaker or porcelain cup. Add one cubic centimeter of the dilute rennet and give a quick stir with the thermometer or shake the beaker in such manner as to give contents a rotary mo- tion. Note the length of time it takes to coagulate. (b) Repeat the experiment with milk just beginning to taste sour or add a small amount of very dilute hydrochloric or sul- phuric acid to the milk. (c) Repeat with milk neutralized with sodium hydroxide. (d) Repeat (a) with sample of the original milk at 95° F., 106° F., 120° F., 140° F., 70° and 60° F. (e) Repeat (a) with the same milk diluted at the rate of 1 part water to 3 of milk. ({ Repeat (e) with 1 part water and 2 parts milk. (g) Repeat (e) with 1 part water and 1 part milk. 96 LABORATORY EXERCISES EXERCISE XXI. Effect of salt and soluble salts on rennet. (a) Action—Make a test of rennet action as in (a) Ex. 20. (b) Repeat (a) with the same milk, three times, adding one per cent. of salt to the milk in the first, 3 per cent. in the second and 5 per cent. in the third test. (c) Repeat (a) with the same milk, adding a small amount of dilute solution of calcium chloride. (d) Repeat (a) with milk heated to 190° F. for 10 minutes and cooled to the usual temperature of 86° F. The Sheppard Ptg. and Pub. Co., Columbus, Ohio One COpy del. to Cat. Diy.