Milk Fermentations. 65 



be associated with the butyric fermentation, but Weig- 

 mann 1 showed that the two conditions were not depend- 

 ent upon each other. He found that the organism which 

 produced the bitter taste acted upon the casein. 



Conn 2 found a coccus form in bitter cream that was 

 able to impart a bitter flavor to milk. The writer sep- 

 arated a lactic acid species from milk that also possessed 

 a similar property. Sometimes a bitter condition does 

 not develop in the milk, but may in the milk products 

 later. Freudenreich 3 separated a micrococcus from cheese 

 that was found to be the cause of bitterness. 



Cream ripened at low temperatures not infrequently 

 develops a bitter flavor, showing that the optimum tem- 

 perature for this type of fermentation is below the typical 

 lactic acid change. 



It has long been a question how to account chemically 

 for the bitter taste in milk. Various ideas have been 

 advanced, but Freudenreich has demonstrated in one case 

 that a bitter substance is formed in the milk that can be 

 isolated by adding alcohol. 



Milk that has been cooked is likely to develop a bitter 

 condition. The explanation of this is that the bacteria 

 producing the bitter substances usually possess endospores 

 and that while the boiling or sterilizing of milk easily 

 kills the lactic acid germs, these forms on account of 

 their greater resisting powers are not destroyed by the 

 heat. 



64. " Sweet curdling 1 " and digesting fermenta- 

 tions. Not infrequently milk instead of undergoing 

 spontaneous souring curdles in a weakly acid or neutral 

 condition, in which state it is said to have undergone 



1 Weigmann, Milch Ztg., 1890, p. 881. 



2 Conn, Kept. Storrs' Expt. Stat., p. 158. 1890. 



3 Freudenreich, Fiihl. Landw. Ztg., 43: 361. 



5-B. 



