FUNCTIONS OF MILK CONSTITUENTS 183 



(2) The soluble calcium salts probably perform 

 some work in assisting in the contraction of the 

 curd. After the curd is formed in the cheese-vat, 

 the milk-sugar remains in the coagulated mass at 

 first, but gradually passes out in solution as the 

 whey exudes from the pieces of curd. The amount 

 of sugar remaining in the curd is much reduced, 

 but the formation of lactic acid continues, thus in- 

 creasing the amount of calcium lactate, acid calcium 

 phosphate, acid calcium citrate, etc. Cheese-makers 

 speak of acid in curd frequently when they really mean 

 whey or, more strictly, milk-sugar contained in whey 

 within the pieces of curd and ready to form lactic acid 

 sooner or later. 



(3) The formation of soluble calcium salts is 

 probably also more or less intimately connected 

 with the changes in the curd during the cheddaring 

 process, when the grain or texture rapidly changes, 

 finally resembling the fiber of the cooked meat on 

 a chicken's breast and when the curd develops the 

 characteristic plastic properties exhibited by form- 

 ing long, silky strings, when brought into contact 

 with a hot iron. This change appears to depend upon 

 the conversion of paracasein into a substance soluble 

 in brine solution (p. 147). 



The conversion of milk-sugar into lactic acid, 

 with consequent formation of increasing quantities 

 of soluble calcium salts, continues quite rapidly 

 throughout the cheese-making process and also in 

 the press and still later in the cheese. Under ordi- 

 nary conditions, the last trace of milk-sugar disap- 

 pears in about two weeks after the cheese is made. 

 But, throughout the process of cheese-making, when 



