178 SCIENCE AND PRACTICE OF CHEESE-MAKING 



cheese ; but its chief functions, in relation to quaHty of 

 cheese, appear to be to give (i) a characteristic mel- 

 lowness of body, (2) smoothness of feeling, (3) rich- 

 ness and delicacy of taste, apart from cheese flavor 

 proper, and (4), in general, palatability. No other 

 constituent can take its place satisfactorily in perform- 

 ing any of these offices. Of course, the high value of 

 milk-fat as a food should not be lost sight of, but this 

 does not necessarily enter into the question of quality 

 of cheese as affected by the presence of fat. The 

 peculiar and exclusive function of milk-fat in giving to 

 cheese certain desirable qualities can be well appre- 

 ciated by comparing dift'erent kinds of cheese, equally 

 well made and differing only in the percentage of fat 

 contained in them, as, for example, cheese made from 

 normal milk containing added cream, cheese made from 

 normal Jersey milk, cheese made from Holstein- 

 Friesian milk, and cheese made from milk skimmed 

 in varying degrees, down to separator skim-milk 

 cheese. 



The relation of fat to yield of cheese will be con-, 

 sidered in detail in the next chapter. 



MILK-CASEIN 



Casein is the constituent of milk which, on ac- 

 count of its peculiar action toward rennet-extract 

 solutions, makes possible the manufacture of ched- 

 dar and many other kinds of cheese. In the pro- 

 cess of cheese-making, it performs two specific 

 functions: (i) In its solidification, its first work is 

 to imprison the fat-globules in the curd and then 

 continue to hold them as firmly as possible through- 

 out the manipulations of cheese-making. (2) Its 



