328 SCIENCE AND PRACTICE OF CHEESE-MAKING 



been considered. We shall later consider its rela- 

 tion to the chemical changes in cheese-ripening. 



Proteins. In cheddar cheese fresh from press, 

 there appear to be different protein compounds, the 

 precise nature of which has not yet been deter- 

 mined. There have been shown to be the follow- 

 ing forms: (i) Protein soluble in warm (122- 

 131 F.), 5 per cent solution of sodium chlorid, 

 which, for convenience, we shall speak of as brine- 

 soluble protein, (2) protein insoluble in brine solu- 

 tion, and (3) proteins soluble in water. The first 

 constitutes the largest amount, often being 75 to 

 90 per cent of the total amount of proteins in ched- 

 dar cheese ; the water-soluble protein is quite fairly 

 constant, varying usually between 4 and 5 per cent 

 of the total proteins, and a part of this is readily 

 accounted for by the milk-albumin in the whey re- 

 tained in the cheese. 



Fat. The fat present in unripe cheese is, in 

 composition and physical condition, essentially 

 milk-fat. 



Milk-sugar. The sugar in newly made cheese is 

 simply milk-sugar in solution in the whey that is 

 retained by the cheese. 



Neutral salts and acid salts. The most promi- 

 nent neutral salt in unripe cheese is calcium lactate, 

 formed as a result of the lactic acid (produced by 

 the fermentation of milk-sugar) upon the insoluble 

 calcium phosphate originally present in the milk, most 

 of which is carried into the cheese-curd and held 

 there. The soluble acid salts present in largest 

 amounts are calcium acid phosphate and, probably, 

 citrate. 



