234 MILK 



Fat-splitting Ferment. A fat-splitting ferment has been found 

 in milk. This is destroyed at 65 C. Recently Rogers has found 

 a. similar ferment in butter. 



Miscellaneous Ferments. A salolase and an enterokinase have 

 been reported, but their actual existence in common market milk 

 is doubted. 



Oxydases and Reductases. Oxidizing and reducing ferments 

 have been constantly found in milk and are of special interest, 

 since they produce reactions by which recently heated milk can 

 be distinguished from raw milk. 



The question whether these enzyms are inherent milk enzyms 

 or bacterial products has not been satisfactorily settled. How- 

 ever, the majority of investigators hold that they are of bacterial 

 origin. This opinion is supported strongly by the fact that milk, 

 when heated to a degree which is destructive to the enzyms, upon 

 standing, again contains these ferments. 



Four 'classes of oxidizing ferments may be distinguished, 

 namely: 



1. Superoxydases, splitting hydrogen peroxid into water and 

 free oxygen. These are also known as catalases. 



2. Oxydases, oxidizing by using the oxygen of the air. 



3. Peroxydases, or indirect oxydases, acting similarly to the 

 true oxydases, but utilizing oxygen liberated from hydrogen 

 peroxid. 



4. Reductases, reducing colored substances and changing sul- 

 phur to hydrogen sulphid. 



Superoxydases differ from peroxydases, inasmuch as they utilize 

 the O 2 resulting from decomposition of two molecules as hydrogen 

 peroxid, while peroxydases utilize O from one molecule of hydrogen 

 peroxid, as shown in the following formulas : 



Superoxydases (catalases) : 2H 2 O 2 = 2H 2 O + O 2 

 Peroxydases: . [H 2 O 2 = H 2 O + O 



Superoxydases act best at a temperature of 37 C.; they are 

 destroyed at 68 C.; are weakened by prolonged heating at 60 C., 

 and may be destroyed by heating at 62 C. for one hour. Heating 

 to 56 C. for three hours partially destroys them. Their action 

 is not inhibited by presence of lactic acid, in which respect they 

 differ from the peroxydases. Superoxydases go into the coagulum 

 when casein is precipitated, and into the cream when cream rises 

 or is obtained by centrifugation. They can be extracted from 

 cream by using water or physiologic sodium chlorid solution. 



Superoxydases are present in large quantity in human milk, 

 especially in the colostrum. In cow's milk they are also con- 

 stantly present, and in excessive quantity when the udder is 



