Milk Fermentations. 59 



58. " Gassy " milks. This very common and undesir- 

 able type of fermentation is caused by the presence of a 

 large number of different bacteria, the majority of which 

 belong to the lactic acid group. The amount of acid 

 formed is always considerably less than that which is 

 present in the typical lactic formation. Besides this, 

 there is also produced as a result of the decomposition of 

 the milk-sugar, various gases such as CO 2 , H, and meth- 

 ane. Accompanying these are also to be noted various 



FIG. 12. A cheese made from "gassy" milk. A severe type of this 

 fermentation. 



other decomposition substances that impart to milk and its 

 products an undesirable flavor and odor. These fermenta- 

 tions are particularly undesirable in cheese-making, as 

 they are the cause of "floating" and "pin-holey 7 ' curds. 1 

 The swelling or huffing of green cheese is invariably due 

 to this type of ferment action. Organisms producing 

 this abnormal change are particularly numerous in ma- 

 nure particles 2 , the colon bacillus (B. coli communisj y 



1 Freudenreich, Landw. Jahr. d. Schweiz, p. 17, 1890. 

 Russell, 12th Kept. Wis, Expt. Stat., p. 139, 1895. 



2 Bolley, N. D. Expt. Stat., Bull. 21. 



