Ripening of Hard Cheeses 427 



lactis. He concludes that there is in this case associative 

 action between Oidium lactis and various species of 

 bacteria. The function of these organisms, as well as 

 of the yeasts that are frequently present, on the ripening 

 of American Brie and Isigny is still a matter of uncer- 

 tainty. 



Hard cheeses. — The growth of molds is excluded in 

 hard cheeses by the strong salt content and the hard- 

 ness and compactness of the rind. Hence, these cheeses, 

 prominently represented by the Swiss Emmenthaler, 

 the English and American Cheddar, and the Dutch 

 Edam, in so far as they are at' all affected by micro- 

 organisms, must depend for their ripening, apart from 

 the enzymes pepsin and galactase, on the action of bac- 

 teria. 



At high temperatures, the numbers of bacteria in 

 hard cheeses evidently decrease more rapidly than they 

 do at lower temperatures, a difference coincident with 

 the rate of ripening. The cheeses kept at the higher 

 temperatures not only ripen more rapidly, and develop 

 a stronger flavor, but soon become over-ripe. It seems, 

 furthermore, that the accumulation of amides and of 

 ammonia goes on for some time after the bacteria had 

 become greatly reduced in numbers. This fact indi- 

 cates, therefore, that if the latter stages of ripening are 

 due to bacteria, they must be carried out by means of 

 enzymes secreted by the organisms. 



It follows, likewise, that at the higher temperatures 

 the bacterial enzymes are produced early in the ripening 

 process in larger amounts, and are, therefore, enabled 

 to accomplish their work more quickly than it is ac- 



