Milk Fermentations. 69 



that is not strongly acid in its reaction. When grown 

 in the light, this germ forms a yellow pigment. In 

 milk, the casein is slowly precipitated and gradually dis- 

 solved. It thrives at a high temperature, from 80-95 F . 



Other cases of red milk have been reported that have 

 been traced to other germs. 1 Menge 2 found a red sar- 

 cina that was the cause of trouble in a milk-supply. 

 Here in this country, it is not at all uncommon to find on 

 old milk, red patches that' are caused by the growth of a 

 yeast-like germ, Saccharomyces glutinis, that is often 

 found in the air. 



67. Blue milk. Blue milk is historically a better 

 known disease than almost any other trouble in milk. 

 As long ago as 1838, Steinhoff showed that the trouble 

 was communicable from one lot of milk to another. It 

 manifests itself in the course of one to three days by the 

 appearance of isolated flecks of bluish or grayish color 

 on the surface of the milk. In fresh milk that is only 

 slightly acid, the gray tints prevail, but as the amount 

 of lactic acid increases in the milk, the blue coloration 

 becomes more marked. So far only one form (Bacillus 

 cyanogenus) is known that is able to produce this change. 

 It does not materially affect the milk, but the butter 

 made from infected cream has very poor keeping quali- 

 ties. In Mecklenburg an outbreak of this disease once 

 persisted for a period of several years 3 . Heim 4 found 

 that this bacillus was especially resistant toward drying, 

 or the influence of chemical agents like soda and potash, 

 but a temperature of 176 F. for a moment sufficed to 

 kill it. 



1 Keferstein, Cent. f. Bakt. I Abt., 21: 177. 



2 Menge, Cent. f. Bakt., 6: 596. 



3 Fleischmann, Book of the Dairy, p. 51. 



4 Heim, Arb. a. d. Kais. Ges. Amte, 5: 518. 



