182 SCIENCE AND PRACTICE OF CHEESE-MAKING 



wherever we find it. It is true, of course, that the 

 presence of water in cheese is masked by the casein 

 and fat and one of the aims of the cheese-maker is 

 to conceal it thus as completely as possible; but this 

 fact has no bearing on the composition or character 

 of the water itself. 



MILK-SUGAR 



The only function milk-sugar appears to per- 

 form in the process of cheese-making is to fur- 

 nish material for making lactic acid. Lactic acid 

 does not remain in milk as free or uncombined 

 acid, but, as fast as formed, it acts upon some of the 

 salts of the milk, especially insoluble calcium phos- 

 phate, combining with a portion of the calcium and 

 forming calcium lactate and soluble or acid calcium 

 phosphate, an acid salt. There are probably other 

 salts in milk acted upon, about the details of which 

 we have not yet obtained complete knowledge. These 

 soluble calcium salts (calcium lactate, and acid cal- 

 cium phosphate, including probably also acid calcium 

 citrate) resulting from the action of acid furnished 

 by the fermentation of milk-sugar, perform several 

 functions in the cheese-making process. 



(i) These soluble calcium salts favor the rapid- 

 ity and completeness of the action of rennet-extract 

 in coagulating milk; in fact, their presence in cer- 

 tain amounts is essential to the action of the ren- 

 net-enzym. Now, while the immediate object of 

 ripening milk in cheese-making is to convert milk- 

 sugar into lactic acid, the real purpose is the forma- 

 tion of soluble calcium salts to hasten rennet 

 coagulation. 



