SO-CALLED 'BIOLOGICAL PROPERTIES' OF MILK 83 



be used as a means of distinguishing cows' milk from human 

 milk. 



Kastle and Porch (1908) found the results of the peroxidase 

 reaction very uncertain with human milk, even with the addition 

 of their sensitiser trikresol ; the colostral stage appeared to have, 

 as a whole, greater activity than the later milk. 



Mechanism of the Peroxidase Reaction. Much work has been 

 done upon the mechanism of the peroxidase reaction. Peroxi- 

 dase is present throughout the animal and vegetable kingdom, 

 but has not been found as a result of bacterial action. 1 The 

 mechanism of this action has aroused the attention not only of 

 dairy chemists but also of botanists and biological chemists. 

 Solutions have been prepared by several investigators from plants 

 and from milk, and there is strong evidence that all these solutions 

 contain small quantities of iron and possibly also traces of 

 manganese. The iron is said to be present in colloidal form, and 

 Sarthou (i, 3) showed that the reaction can be brought about when 

 the solution contains as small an amount as -0002 per cent, of iron.* 

 Other investigators, who have incidentally confirmed the results 

 obtained by the above authors, have shown that the reaction was 

 of the same nature as that of a metallic sol and that, although 

 the solution was inactivated by boiling, it could be reactivated 

 by appropriate methods, such as the addition of platinsol, or by 

 projecting milk in a fine jet at a high pressure on to an agate plate, 

 or by the addition of pumice. 8 Rohman and Shmamine believe 

 that iron and other salts, as also certain organic bodies, have an 

 affinity for hydrogen peroxide, to which they become attached. 

 They believe that this probably occurs also with organic peroxides, 

 and that this method of action may account for the action of the 

 iron in the peroxidase reaction. 



Some discussion has occurred between Grimmer (2, 3, 4, 6) and 

 Kooper (i, 2, 3, 4) and Hesse and Kooper (i, 2, 3) in regard to the 

 method of action of the peroxidase in milk. Kooper and Hesse 

 worked with Rothenfusser's reagent, and believed that the reaction 

 was dependent upon the alkalinity of the milk. Grimmer did not 

 agree with this suggestion, and believed that the reaction was 

 produced by a ferment, and that this ferment was connected with 

 the albumin fraction of the protein in milk. The discussion has 

 been continued for a considerable period, and neither of the authors 

 appears to be convinced by the arguments of the other. Grimmer 

 agrees that the reaction is affected by the alkalinity or acidity of 

 the milk before boiling, but that it depends in reality upon the 

 denaturalisation of the albumin. 



Several observers have investigated the possibility of this 

 reaction being due to bacteria present in the milk, but all have 



1 Cp. Fred and others. 



1 Cp. also Bertrand (i, 2), Van der Haar, Moore and Whitley. 



3 Cp. Engler and Wohler, Bordas and Touplain, and Meyer. 



G z 



