360 SCIENCE AND PRACTICE OF CHEESE-MAKING 



was removed and the curd was put in press. The 

 peculiar behavior of the curd during the cheddaring 

 process is probably due to the formation of the 

 brine-soluble substance; and the formation of this 

 substance appears to be associated, at least in consider- 

 able measure, with the formation of soluble lime salts 

 resulting from the action of lactic acid. From some 

 work done at the New York experiment station, it 

 seems that when this brine-soluble compound is not 

 formed, we do not get water-soluble substances, 

 and this means that we get no cheese-ripening. In 

 other words, the formation of the brine-soluble sub- 

 stance appears to be prerequisite to further ripening 

 changes. 



Reviewing briefly the action of acid in cheese-mak- 

 ing and cheese-ripening, its chief work appears to be 

 combination with the insoluble lime salts of the 

 milk, producing calcium lactate and calcium acid 

 phosphate. These compounds, in conjunction with 

 the degree of heat used and, perhaps, also in asso- 

 ciation with the action of rennet-enzym, produce 

 marked changes in the curd in respect to body, 

 texture and solubility in brine solution. In the 

 cheese-making process, the insoluble portion of 

 the curd begins to change into a form that is soluble 

 in warm, 5 per cent brine, this change taking place 

 rapidly during the cheddaring operation and con- 

 tinuing until all the protein of the curd is in this 

 form; the change appears to be complete 9 or IO 

 hours after the curd is put in press. Then this 

 brine-soluble curd begins to change into an in- 

 soluble form, this reverse change going on very 

 rapidly for a few hours and then more gradually for 

 many months. From this insoluble form appear to 



