84 MILK AND ITS HYGIENIC RELATIONS 



failed to obtain the reaction in bacterial cultures so far investigated, 

 although it was shown by Jensen to be present inside the cells of 

 Oidium Lactis and Penicillium Glaucum. 1 



A good deal of work has been done in order to ascertain which 

 of the constituents of the milk was primarily concerned with the 

 reaction. Observers are to some extent divided in their opinion as 

 to whether the caseinogen or the albumin is primarily concerned, but 

 it would appear that the latter is the one most probably connected 

 with the production of this effect, Thus Klebs, Raudnitz (2, 3, 4), 

 Barthel (i), Bordas and Touplain (i, 2) believed that caseinogen was 

 concerned in the peroxidase reaction, while Kowalewsky believed 

 that it was connected with lactalbumin. Monvoisin found the 

 reaction positive in the nitrate obtained after saturation with 

 magnesium sulphate. Meyer showed that the reaction was not 

 given by caseinogen alone, but that a positive reaction was obtained 

 with cream from centrifuged milk as well as with the milk remaining 

 behind, and also slightly with the sediment. Kooper (i) did not 

 obtain the peroxidase reaction with cream, and Sames showed that 

 the reaction was strongest in the first milk (that poorest in cream) and 

 was often absent in the strippings (that richest in cream.) Sames 

 also showed that the reaction was probably connected with the 

 albumin fraction. Grimmer (i) showed that a solution prepared 

 by saturating whey with ammonium sulphate, and subsequently 

 dissolving the precipitate thus obtained, gave a strong peroxidase 

 reaction. 



The Effect of Heat upon the Peroxidase Reaction. In using 

 this reaction for the purpose of detecting the previous heating of 

 milk, it is necessary to know at what temperature this reaction ceases 

 to be given. The numerous observations upon this point are by 

 no means concordant. It is not possible to deal in detail with the 

 various results obtained, but the accompanying table, compiled in 

 great measure from the tables given by Waentig (2) (1907) and van 

 Eck (1911), will show the most essential points. It illustrates the 

 great difficulty of deciding upon the precise temperature at which the 

 reaction ceases to be given, and therefore the exact temperature 

 to which the milk may be considered to have been heated. 



Van Eck (1911) arranged a series of test-tubes containing varying 

 amounts of raw and sterilised milk. (The sterilised milk was heated 

 to 100 C. for half an hour.) The series ranged from 9-9 c.c. sterilised 

 milk and 'I c.c. raw, to 8 c.c. raw and 2 c.c. sterilised. After adding 

 equal amounts of the reagent (Storch's test was used), these tubes 

 formed a scale of colour which was used for each experiment as a 

 standard colour scale, the colour depending upon the amount of 

 fresh milk that is, upon the amount of ferment present in each tube. 



He then took some of the same milk and heated it gradually 

 in a water-bath fitted with a stirrer, and, taking samples at different 



* Cp. also Bellei. 



