94 MILK AND ITS HYGIENIC RELATIONS 



and Staub, Gerber and Ottiker, Kooper (2, 3), Harden and Lane- 

 Clay pon. 



Kooper showed that the results obtained by the different 

 apparatus were not identical, and he endeavoured to obtain a 

 correction factor for the different methods, but without appreciable 

 success. 



In dairy produce Lobeck's apparatus x appears to be the most 

 widely used. The disadvantage of this apparatus lies in the absence 

 of facilities for adequate shaking, which tends to give inaccurate 

 results. For ordinary dairy purposes the estimation need only be 

 correct within certain limits, but it is doubtful how far the dairy- 

 man, in this country at any rate, places any reliance upon the 

 estimation of catalase in determining the quality of the milk. 



Sources of the Catalase found in Cows' Milk. The estima- 

 tions of the catalase content of milk showed that the amount of 

 catalase increased when the milk was kept. Chick's work, already 

 referred to, had indicated bacteria as a probable source of catalase 

 in milk. Several observers have investigated the formation of 

 catalase by bacteria, and have shown that a large number of these 

 organisms produce this enzyme in the course of their growth. 



Seligmann (i, 2, 4) isolated from milk a strain of cocci which 

 produce large quantities of catalase on being cultured. Koning 

 showed that bacteria will produce catalase, and found, further, that 

 these bacteria would not produce peroxidase, and hence deduced that 

 catalase and peroxidase were different enzymes. Jensen found 

 that a number of organisms would produce catalase. Sarthou (2), 

 Kooper (i, 2), and Faitelowitz all showed that the catalase content 

 of milk increases with the age of the milk, and they believed that 

 this was due to the formation of catalase by bacteria. 



Sarthou showed that catalase was formed if, after heating, 

 the milk was inoculated with a lactic-acid-forming organism, and 

 Kooper found that milk collected initially with full precautions 

 against bacterial contamination had a lower content of catalase. 

 If, however, such carefully collected milk was contaminated by 

 the addition of a small piece of solid excreta, the catalase content 

 rose very greatly. Further, he showed that catalase could be pro- 

 duced in boiled milk, if such milk was inoculated with raw milk. 



The increase of catalase in milk can be inhibited by the addition 

 of antiseptics, which are well known to prevent the growth of 

 bacteria. Faitelowitz used chloroform and formalin for demonstrat- 

 ing this fact, and Barthel (3) and Smidt (2), working independently, 

 showed that although the milk was rendered sterile by antiseptics, 

 catalase was still present, and they believed that probably there 

 was some other source of this enzyme, apart from bacteria. The 

 milk used by these observers is not stated to have been germ-free. 

 In order to establish the presence of any original catalase 



1 Cp. Gerber and Ottiktr. 



