294 



MANUAL OF MILK PRODUCTS 



facture of cheese, but those which are of greatest value are the 

 milk-fat and casein. These two solids constitute over 90 per 

 cent of the solids in the cheese. Small amounts of albumin, 

 milk-sugar, and other solids are retained in the cheese, but 

 these are so small that they do not appreciably affect the yield. 

 It is evident from the above that the yield of cheese will be 

 influenced primarily by the amount of fat and casein in the 

 milk, other conditions being equal. In general, the percentage 

 of casein in milk follows a quite definite relation to the per- 

 centage of fat. In other words, milk rich in fat is also rich in 

 casein, while milk low in fat is also low in casein ; but the ratio 

 between these two constituents is not exactly constant. In 

 the richer milks, while the percentage of casein is also increased, 

 it does not increase in exactly the same degree as does the per- 

 centage of fat. This means that in rich milk the ratio of the 

 casein to the fat is slightly lower than in milk lower in fat- 

 content. This is shown by the following table by Van Slyke 

 and Publow : x 



Per Cent op Fat in Milk 



Per Cent op Casein in Milk 



Ratio op Fat : Casein 



3.00 



2.10 



1 : 0.70 



3.25 



2.20 



1 : 0.68 



3.50 



2.30 



1 : 0.66 



3.75 



2.40 



1 : 0.64 



4.00 



2.50 



1 : 0.62 



4.25 



2.60 



1 : 0.61 



4.50 



2.70 



1 : 0.60 



5.00 



2.90 



1 : 0.59 



Since the percentage of fat is the most variable solid in milk, 

 the yield of cheese should be in nearly direct ratio to the fat- 

 content of the milk. The effect of fat on the yield of cheese is 

 shown by Van Slyke 2 as follows : 



1 Science and Practice of CheesemaMng, p. 172, Orange Judd Co. 



2 New York Exp. Sta. Bui. 308. 



