EXERCISE 82 



MILK TESTING 



Statement. Before the Babcock method of testing milk was discovered milk was purchased by the 

 gallon or pound without regard to its richness. Thus, for example, milk which contained a small 

 amount of butter fat brought as much as that which contained a great amount of fat. Now most 

 of the milk sold on the market is tested for fat, and its value is determined by its fat content and its 

 freshness and cleanliness. In a word, milk is now sold on its merits. The dairyman who takes 

 the pains necessary to produce rich, clean milk is rewarded, and the careless dairyman is penalized. 



Object. To test different milk samples and milk products. 



Materials. Babcock tester, milk-testing bottles, and cream-testing bottles; sulphuric acid 

 (commercial, Sp. Gr. 1.82); 17.5-cubic-centimeter, 18-cubic-centimeter, and 17.6-cubic-centimeter 

 pipettes; milk, cream, and cheese to be tested. 



Directions. To test for butter fat in milk proceed as follows : Clean a milk-test bottle (graduated 

 from 1 to 10) and a 17.6-cubic-centimeter pipette. By suction draw into the pipette 17.6 cubic cen- 

 timeters of milk to be tested. In securing the sample be careful that the milk is well stirred, so that the 

 sample tested will be representative of the entire amount. Holding the milk-test bottle at an angle let 

 the milk run from the pipette into the bottle. In like manner, with the 17.5-cubic-centimeter pipette 

 add commercial sulphuric acid. Let it run down the neck of the bottle so as to wash down any milk 

 that may be in the neck. Holding the bottle by the neck give it a gentle rotary motion until the acid 

 and milk are mixed. When mixed properly they should have a rich chocolate-brown color. Repeat for 

 other samples. Place the bottles in the tester and whirl for five minutes at the speed indicated on the 

 tester. Fill each bottle to the neck with warm water and whirl again for two minutes. Add warm 

 water until the butter fat stands in the bottle neck and whirl again for one minute. Remove and 

 read the test. 



For testing skim milk, where it is desirable to read the small fractions of 1 per cent, two forms of 

 bottles have been devised. In one two pipettes full of milk are used and the graduations have half the 

 ordinary value ; in the other the bottle has two necks, one for the introduction of milk and acid, and the 

 other, extremely narrow in size, in which the fat is measured. The ordinary milk-test bottle may be used 

 if neither of these can be had. 



1. Test a milk sample taken from the first milk drawn from a cow and a sample taken from the 

 milk last drawn. 



2. Test milk from a Jersey cow, a Holstein, a Guernsey, an Ayrshire, a Shorthorn, a Hereford. 



3. Test a sample of buttermilk. 



4. Test a sample of skim milk taken (1) from milk skimmed by hand and (2) from separated 

 milk from different separators in the community. 



5. Test cream in the same manner as milk, only use an 18-cubic-centimeter pipette and a cream- 

 test bottle, which is graduated to 35 per cent or more. 



6. Test butter and cheese for butter fat, only weigh out 18 grams instead of measuring. Place 

 it in the bottle, add a little water and then add acid to dissolve it. Proceed as in the case of milk. 



Questions. In what way does the acid affect the milk? What should a good sample of milk test? 

 What is the value of testing milk? How does the creamery determine the value of the cream pur- 

 chased ? Is there any advantage in the farmer's allowing a large amount of milk to go to the creamery 

 with the cream? Does he lose the milk? How might he save a part of it? 



References. Waters, H. J. Essentials of Agriculture, pp. 372-379. Ginn and Company. Eckles and 

 Warren. Dairy Farming, pp. 59, 196-199. The Macmillan Company. Stocking, W. A. Manual of Milk 

 Production, pp. 109-136. The Macmillan Company. 



r 162 1 



