THE ENZYMES OF MILK 



243 



Russell discovered that the proteins of milk underwent 

 proteolytic disintegration even in the presence of ether, 

 chloroform and other compounds which inhabit the growth 

 of bacteria. Milk which contained on an average 20 

 per cent, of its proteins in a soluble form after being 

 kept for three or four weeks in vessels to which antiseptics 

 had been added to prevent bacterial action, was found 

 to contain 38 per cent, of its proteins as albumoses and 

 peptones. Milk which has been heated to a temperature 

 sufficient to destroy enzymes does not undergo such 

 changes. Subsequent investigation showed that the 

 proteolytic decomposition of milk obtained and kept 

 under aseptic conditions was due to the presence in it 

 of a trypsin-like enzyme, to which the name oigalactase 

 has been given. 



The amount in milk is very small, and although at 

 first it was thought that it played a major part in the 

 ripening processes of cheese, its influence in this direction 

 is now known to be comparatively slight. 



Traces of lipase, diastase, and other enzymes are said 

 to occur in milk, but the evidence for the statement is 

 not very convincing. 



Positive results are readily obtained with tests for 

 peroxidases (p. 115), but whether they are caused by 

 galactase only or by other types of enzymes is not 

 known with certainty. 



Since the enzymes in milk are destroyed when the 

 latter is heated for a short time to 80 C. the presence 

 or absence of reaction with tincture of guaiacum or 

 paraphenylendiamine and hydrogen peroxide affords a 

 ready means of distinguishing boiled from fresh milk. 



In some countries where regulations are enforced with 

 a view of checking tuberculosis among farm stock, the 



