FUNCTIONS OF MILK CONSTITUENTS 185 



depend largely for the active part which they take 

 in cheese-making upon the presence of lactic acid, 

 by which insoluble calcium salts are converted into 

 soluble forms, especially soluble calcium phosphate. 

 When we determine the acidity of whey at various 

 stages of the operations of cheese-making, we are 

 really measuring directly the formation of acid com- 

 pounds, which furnish, of course, a measure of the 

 amount of lactic acid that has been formed. 



It has been noticed that, when in the making of 

 cheese a higher degree of acidity is produced, while 

 the curd is still in the whey, that the amount of ash 

 in the cheese is less than when so much acid is not 

 formed. This is in accordance with what one would 

 expect, since the more rapidly the insoluble calcium 

 salts are dissolved while the curd is in the cheese-vat, 

 the larger is the amount of soluble salts going into 

 the whey. 



