CHAPTER XIX 

 TESTING 



IN connection with marketing, a certain amount of 

 testing of the products should be practiced, to determine 

 exactly the results and grades of products. This includes 

 the testing of the whole milk, whey and cheese for fat, 

 the milk for casein, and the cheese for moisture. In 

 factories in which the milk is bought on the fat basis, 

 it is necessary to test each patron's milk for fat. If there 

 is a cheese-moisture law in the state, it is necessary to 

 test for moisture. The whey should be tested to learn 

 the loss of fat in the manufacturing process and to ascertain 

 whether the losses have been reduced to the minimum. 



308. The fat test. The test commonly used to de- 

 termine the fat in milk is known as the Babcock. The 

 principle of this test is as follows : Fat exists in the form 

 of very small globules. Because the fat globules are lighter 

 than the other milk constituents, under the influence of 

 the force of gravity most of them rise to the surface. 

 There, mixed with the other milk substances, these glob- 

 ules form a layer of cream. Babcock found that by add- 

 ing to the milk sulfuric acid of proper strength and 

 temperature, the casein, the milk-sugar and the albumin 

 are decomposed and the sticky quality of the milk is 

 destroyed. The acid does not decompose the fat but 

 leaves it free to come to the surface of the mixture. Under 



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