376 



Effective Farming 



FIG. 149. A four-bottle hand power tester. 



Milk from different cows varies considerably from this aver- 

 age, however, the greatest difference being in the percentage 

 of butter-fat, some cows giving milk low in fat and others high 



in fat. The parts of 

 milk other than water 

 are known as milk 

 solids, or as total 

 solids, and the solids 

 other than butter- 

 fat, as solids not fat. 

 The milk minus the 

 fat is known as the 

 milk-serum, or as the 

 milk-plasma. As 

 shown by its composition, milk contains all the five food 

 groups and is a balanced food product. 



The fat of milk rises as cream. It is an emulsion of globules 

 so small that a single drop contains more than a hundred 

 million. Even from the same cow the 

 globules are not all of the same size; 

 some may be two or three times as large 

 as others. The average size depends 

 largely on the breed of cow. 



The protein is chiefly of two kinds, casein 

 and albumin. Casein is the chief constitu- 

 ent of cheese. Albumin of milk is some- 

 what like the white of egg. When whey is 

 heated to 160 F., the albumin coagulates. FIG. 



Milk-sugar, the carbohydrate of milk, 

 is less sweet than cane-sugar. It is used 

 extensively for the modification of cow's 

 milk for infants and is the most readily digested of all sugars. 

 The ash, or mineral matter of milk, consists chiefly of the 

 chlorides and phosphates of sodium, potassium, magnesium, 

 and calcium. 



150. A type of 

 steam tester with an 

 arrangement for heat- 

 ing the water used in 

 the test. 



