BACTERIA IN CHEESE-MAKING. 26/ 



bacterial growth, and it seems strange that the putrefaction 

 does not more commonly occur. Such decay does sometimes 

 occur, beginning perhaps in the center and eventually involv- 

 ing the whole mass, until the cheese becomes a soft, vile- 

 smelling mass of slime. That the trouble is due to bacteria 

 is evident, of course, from the fact that all putrefaction is thus 

 caused. Why it occurs in some cheeses and not in others is 

 not known. It is most likely to be found if the cheeses are 

 kept at too low a temperature. 



Some of the common imperfections in cheese-ripening are 

 characterized by the appearance of colored spots in the cheese. 

 Red spots are quite common, chiefly on the surface ; black spots 

 are sometimes found, and even blue spots are described among 

 the troubles arising in the cheese-ripening. Each of these has 

 been studied sufficiently to show that they are ordinarily 

 caused by microorganisms. The black spots are commonly 

 attributed to a mold-like organism, the red and blue spotting to 

 bacteria. An imperfection in cheese-ripening, recently studied 

 by Harding, characterized by the development of a sweet flavor, 

 has been found to be due to a species of yeast. 



These do not by any means exhaust the list of cheeses ripened 

 abnormally through the action of undesirable organisms. 

 The list is a long one and bacteriologists have as yet only 

 touched the subject incidentally, without even attempting any- 

 thing like a systematic study. A sufficient number have been 

 mentioned to serve our purpose, showing how closely the 

 ripening of cheese is dependent upon the species of micro- 

 organisms present in the cheese. We must conclude, not only 

 that the proper ripening is dependent upon the presence of 

 proper microorganisms in the milk, but that the presence of 

 an undue number of miscellaneous bacteria is almost sure to 

 result in some type of abnormal ripening, producing one of 

 the numerous "off" flavors, if nothing more serious. 



Cheese Poisoning. Mention should also be made here of a 



