CHAPTER XV 



Conditions Affecting Proportions of 

 Constituents in Milk 



In studying- the composition of milk from dif- 

 ferent cows or herds, one of the first facts noticed 

 is that the same constituents vary in amount more 

 or less widely in different milks. This fact is of 

 the highest importance in studying the relations 

 of milk to cheese-making. As a foundation for 

 a more detailed consideration of these relations of 

 milk, it seems desirable that we should study with 

 some degree of fullness the more important condi- 

 tions which cause variation in the amounts of 

 constituents of milk. Those constituents of great- 

 est interest to us which vary most are fat and 

 casein. Milk-sugar and salts vary only slightly 

 as compared with the amount of variation in fat 

 and casein. We shall find it to be a matter, not 

 only of interest, but of practical importance, to study 

 the extent of these variations and their causes, 

 and also to learn to what extent different influences 

 affect the relation of fat to casein. As we shall 

 show later (p. i86), the percentages of fat and 

 casein in milk largely determine the yield of cheese ; 

 while the proportion of these two constituents, relative 

 to each other, determine the composition (p. 231) 

 and to a considerable degree, the quality of cheese 



(p- 243). 



155 



