Putrefactive Fermentations 117 



almost wholly because the taste is unpleasant to 

 the ordinary palate. A large amount of lactic acid 

 is, perhaps, injurious to young and delicate or weak 

 digestive organs, but ordinarily is harmless. Lactic 

 acid fermentations are extremely important in the 

 processes of both butter and cheese manufacture, 

 and their relations to these processes will be dis- 

 cussed in detail in the proper place. 



Fermentations affecting the albuminoids. These in- 

 clude ordinary putrefactive fermentations, peptogenic 

 fermentations, and fermentations resulting in the for- 

 mation of poisonous products. These fermentations, 

 as a rule, do not thrive in the presence of a strong 

 lactic fermentation, so that ordinarily they do not 

 manifest themselves in milk unless the conditions are 

 peculiarly favorable for their development and un- 

 favorable for the development of lactic acid. Many 

 of the putrefactive fermentations will go on at a 

 lower temperature than the lactic fermentations do ; 

 hence it is often found, when milk is kept at a low 

 temperature in order to keep it from souring, that 

 after a certain time it becomes bitter or foul -smell- 

 ing. This condition is caused by some one of the 

 characteristic putrefactive fermentations. The putre- 

 factive germs also readily take on the spore form, 

 and in this condition are not so readily killed by 

 heat. The putrefactive fermentations usually result 

 in the formation of bitter or other unpleasant flavors 

 and disagreeable odors, and they are frequently ac- 

 companied by a considerable evolution of gas. Pep- 

 togenic fermentations are those which exert a pep- 



