Composition of Milk and Its Products. 19 



tity of albumen which colostrum contains, it will coagu- 

 late on being heated toward the boiling point. In the 

 course of four or five days the secretion of the udder 

 gradually changes from colostrum to normal milk; the 

 milk is considered fit for direct consumption or for the 

 manufacture of cheese and butter, when it does not co- 

 agulate on boiling and is of normal appearance as re- 

 gards color, taste, and other properties. For composi- 

 tion of colostrum milk, see Appendix, Table I. 



24. Composition of milk products. In addition to 

 its use for direct consumption, milk is the raw-material 

 from which cream, butter, cheese, and condensed milk 

 are obtained. 



When milk is left standing for some time or subjected 

 to centrifugal force, it will separate into two distinct 

 parts, cream and skim milk. The proportion of each 

 part which is obtained, and their chemical composition, 

 will depend on the method by which the separation is 

 effected; in the so-called gravity process where the 

 cream is separated on standing either in shallow pans 

 in the air, or in deep cans, submerged in cold water a 

 less complete separation is reached, since the skim milk 

 obtained is richer in fat than when the separation takes 

 place through the action of centrifugal force. 



The milk is now always in modern creameries skimmed 

 by means of cream separators. Separator cream will 

 contain from 15 to 50 per cent, of fat, according to the 

 adjustment of the separator and of the milk supply; 

 ordinarily it contains about 55 per cent, of fat. Cream 

 of average quality, in addition to the fat content given, 

 consists of about 66 per cent, of water, 3.8 per cent. 



