Bacteria in the Cheese Industry. 161 



is acid. This undoubtedly explains the contradictory re- 

 sults obtained in the ripening of cheese made from pas- 

 teurized milk, such cheese occasionally breaking down 

 but in an abnormal manner. 



The previous results as to the failure of cheese to ripen 

 when treated with disinfectants, experiments which were 

 supposed to be the foundation of the bacteriological 

 theory of cheese-ripening are now explainable on a 

 new basis. The casein is not peptonized because these 

 strong disinfectants destroy the activity of the enzyme 

 as well as the bacteria. Where chemicals such as ben- 

 zol, chloroform, ether, and toluol are used, bacterial growth 

 is inhibited, but enzyme action is still possible. In the 

 presence of these, green cheese undergoes the normal 

 peptonization of the casein. 



1 70. Flavor of cheese. While the action of this fer- 

 ment is exerted on the decomposition of the casein, it is 

 not yet known what its relation is to the production of 

 proper flavors in cheese. Acting as it does on the nitrog- 

 enous compounds of the milk, it has a marked effect on 

 the texture of the ripened cheese. 



The manner in which the peculiar flavors that charac- 

 terize the various kinds of cheese are produced is yet an 

 unsolved problem. The view that is most generally ac- 

 cepted is that this most important phase of cheese cur- 

 ing is dependent upon bacterial activity, but the organisms 

 that are concerned in this process have not as yet been 

 satisfactorily determined. In a number of cases, differ- 

 ent species of bacteria have been separated from milk and 

 cheese, that have the power of producing aromatic com- 

 pounds that resemble in some cases, the peculiar flavors 

 and odors that characterize some of foreign kinds of 

 cheese; but an introduction of these into curd has not 



ii B. 



