THE MILK IN ITS RELATION TO CHEESE 9 



on the quality of the cheese. Many of the details of 

 cheese-making processes have been developed to prevent 

 the loss of fat in manufacture. The yield of cheese is 

 almost directly in proportion to the amount of fat in the 

 milk; nevertheless, because the solids not fat do not in- 

 crease exactly in proportion to the fat, the cheese yield 

 is not exactly in proportion to the fat. The fat, however, 

 is a good index of the cheese-producing power of the milk. 

 12. Casein. Cheese-making is possible because of 

 the peculiar properties of casein. This is the fundamental 

 substance of cheese-making because it has the capacity 

 to coagulate or curdle under the action of acid and rennet 

 enzymes. Casein is an extremely complex organic com- 

 pound. 1 Authorities disagree regarding its exact com- 

 position, but it contains varying amounts of carbon, 

 oxygen, nitrogen, hydrogen, phosphorus and sulfur, and 

 it usually is combined with some form of lime or cal- 

 cium phosphate. It belongs to the general class of 

 nitrogen-containing compounds called proteins. It is 

 present in milk in the form of extremely minute gelat- 

 inous particles in suspension. Casein is insoluble in 

 water and dilute acids. The acids, when added, cause 

 a heavy, white, more or less flocculent precipitate. 

 Rennet (Chapter III) causes the casein to coagulate 

 (curdle), forming a jelly-like mass called curd, which is 

 the basis of manufacture in most types of cheese. In 



1 Van Slyke, L. L., and A. W. Bosworth, Composition and 

 properties of some casein and paracasein compounds and their 

 relations to cheese, N. Y. Exp. Sta. Tech. Bui. 26, 1912. 



Forbes, E. B., and M. H. Keith, A review of the litera- 

 ture of phosphorus compounds in animal metabolism, Ohio 

 Exp. Sta. Tech. Bui. 5, pages 32-36, 42-45. 



Van Slyke, L. L., and A. W. Bosworth, Condition of casein 

 and salts in milk, N. Y. Exp. Sta. Tech. Bui. 39. 



