68 ABNORMAL MILK 



Colostrum will show reddish cream on the surface, but no blood- 

 like material will separate out. 



Blue Milk. Blue milk is quite commonly found. Formerly 

 it was thought that this color was due to the condition of the 

 casein in the milk, but since more has been discovered in regard 

 to the effect of germ life upon conditions and properties of milk, 

 it has been proved that blue milk is caused by bacteria 1 (Bacillus 

 cyanogenus). This particular germ produces the blue color in 

 the milk only when the milk has an acid reaction. When sterile 

 milk is inoculated with this particular germ, the blue color is not 

 produced, but by the addition of a little acid, or by inoculating 

 the milk with the bacteria that produce lactic acid, the blue color 

 is produced. This seems to be one of the instances of symbiotic 

 action of bacteria in milk. There are probably other causes, 

 but they are not known. This germ, according to Aikman, is 

 killed by heating the milk to about 176 F. The germ ceases to 

 work as soon as milk is coagulated. 



Yellow Milk. According to Aikman, 1 yellow milk is caused 

 chiefly by one species of bacteria, named Bacillus synxanthus. 

 This micro-organism belongs to the group of ferments that act 

 upon the fat of milk. There are different shades of yellow pro- 

 duced in milk, caused by different species of bacteria, but the 

 above-mentioned one is considered to be the principal cause. 

 Some produce a brilliant yellow color, while other species first 

 curdle the casein, and then digest or dissolve it into a yellow or 

 amber-colored liquid. 



Ropy Milk. Slimy or ropy milk is not common, but is 

 sometimes encountered by milk-dealers and is caused by certain 

 micro-organisms. Aikman mentions the fact that no less than 

 eighteen different and distinct organisms have been identified as 

 associated with this slimy fermentation. Most of the investi- 

 gators agree that two organisms are chiefly responsible for the 

 slimy condition. One of these is Bacillus lactis viscosus, 2 which 

 grows best in the presence of air and neither forms acid nor thrives 

 in an acid medium. This germ has been found to be frequently 



1 C. M. Aikman, in " Milk, Its Nature and Composition." 



2 Adametz, Landw. Jhr., 1891, p. 185. 



