170 E.KPORT OF THE ChEMICAL DePAKTMENT OF THE 



were present only in small numbers. Even when large numbers 

 were added to milk before making it into cheese, these bacteria 

 ceased to grow almost as soon as the curd was put into the 

 press and rapidly disappeared in the cheese. 



It was found that from the time cheese was made until fully 

 ripened there were present few besides lactic acid bacteria, so 

 called because they curdle milk by production of acid without 

 subsequent digestion of the casein. From these results von 

 Freudenreich was led to question the connection between 

 enzyme-forming bacteria and ripening process. He made numer- 

 ous attempts to produce cheese with the addition of cultures 

 of enzyme-forming bacteria, which uniformly resulted in a 

 product of poorer flavor, according to his opinion. He then 

 became the champion of the theory that lactic acid bacteria are 

 the principal, if not the only, cause of cheese ripening.^ 



The chief objection to this theory is the fact that no one has 

 yet been able to demonstrate the production of an enzyme on 

 the part of lactic acid bacteria. Without such aid it is difficult 

 to understand how a becterium is to attack an insoluble sub- 

 stance such as the coagulated casein in cheese. 



Von Freudenreich' added chalk to milk cultures of these lactic 

 acid bacteria for the purpose of preventing the accumulation of 

 acid and of simulating in this respect the conditions found in 

 cheese. He was thus able to demonstrate the ability of these 

 organisms to increase materially the amount of soluble nitrogen. 

 However, Chodat and Hofifman-Bang^ have pointed out that 

 this is not equivalent to attacking the casein after it has been 

 coagulated by rennet. They maintain that lactic acid becteria 

 are unable to attack coagulated casein, even when sugar is not 

 present. 



In a later publication Jensen,^ without bringing forward 

 adequate experimental evidence, has suggested that lactic acid 

 bacteria are able to elaborate an enzyme. 



•v. Freudonreich. Cent. f. Bak., II Abt., 1:384 (ISOH). 

 'v. Freudenreich. Cent. f. Bak.. II Abt.. .3;2.31 (1897). 

 •Chodat and IIoffman-Bans. Ann. In^t. Basteur. l."):3G (1901). 

 'Jensen. Landw. Jahrb. d. Schweiz., 14:197 (1900). 



