356 SCIENCE AND PRACTICE OF CHEESE-MAKING 



2. Rennet-enzym. 



3. Galactase. 



4. Micro-organisms, commonly bacteria. 



Just what part is played by each agent in the forma- 

 tion of water-soluble proteins and derived proteins, 

 or what interdependence there may be of the work 

 of one agent upon the products of the work of 

 another, we are at present able to say only in part, 

 and not very definitely at that. We will now present 

 an outline of what we may conceive as the distribu- 

 tion of work among these different agents in the light 

 of the experimental results that are now available. 

 We are conscious of the possibility, or rather prob- 

 ability, that some of these statements will need 

 revision in the near future. 



ACTION OF ACIDS IN CHEESE-RIPENING 



The necessity of the presence of some acid in milk 

 and in cheese-curd during the process of making 

 cheddar cheese seems to have been well established, 

 since cheese made without acid fails to ripen satis- 

 factorily. In the absence of acid, little or no brine- 

 soluble protein or water-soluble substance is formed, 

 even after long periods of time. The work of acid, 

 whatever may be the way in which its specific influ- 

 ence is exerted in cheese-ripening, is something like 

 this: Lactic acid is formed by the action of micro- 

 organisms upon milk-sugar during the process of 

 cheese-making; and its formation continues not only 

 during the time the curd is in the cheese- vat but 

 also in the curd as it is put in the press and later. 

 Under normal conditions, the acid continues to be 

 formed so long as any milk-sugar remains in the 



