Milk Fermentations. 67 



principle from a number of different species. Duclaux 1 

 has given to this digesting enzyme the name casease or 

 cheese ferment. These isolated ferments when added to 

 fresh milk possess the power of causing the characteristic 

 curdling and subsequent digestion quite independent 

 of cell development. The quantity of ferment produced 

 by different species differs materially in some cases, the 

 amount of rennet ferment being so imperceptible as 

 to be obscured in the reaction by the digestive process. 



In these fermentations, the chemical transformations 

 are profound, the complex proteid molecule being broken 

 down into albumoses, peptones, amido- acids (tyrosin and 

 leucin), and ammonia as well as fatty acids. 



Not infrequently these fermentations gain the ascend- 

 ency over the normal souring change, but under ordinary 

 conditions they are repressed, as they are unable to tolerate 

 the lactic acid group. They are, however, present in all 

 milks to a greater or less extent, as can be seen from the 

 fact that boiled, sterilized, or -pasteurized milks invari- 

 ably undergo this type of fermentation on account of the 

 resistance of the spore-bearing species that remain in the 

 milk after the lactic forms are killed. 



They are present in milks to a larger extent in summer 

 than winter, on which account it is much more difficult 

 to sterilize milk thoroughly during this season. Germs of 

 this class are not only undesirable if they gain the as- 

 cendency in milk, but where milk is made up into cheese, 

 considerable loss occurs from the digestion of the casein, 

 the peptonized portions being lost in the whey. 



65. Soapy milk. Weigmann and Zirn 2 isolated from 

 a milk having a soapy flavor, a specific germ, B. lactis 

 saponacei, capable of imparting a taste of this sort. Milk 



1 Duclaux, Le Lait. p. 121. 



2 Weigmann and Zirn, Milch Zeit., 22: 569. 



