ENZYMS IN MILK 235 



diseased. A test for catalase has, therefore, been used to indicate 

 mastitis. Seligmann thinks that the large amount of catalase in 

 colostrum is derived from the leukocytes, since these are present 

 in large numbers. In milk from diseased udders their presence 

 also suggests leukocytes as the origin. The catalases of normal 

 milk are probably the product of saprophytic bacteria. 



There is the possibility of superoxydases being inherent milk 

 enzyms, but convincing proof of this is lacking. We know that 

 there are bacteria, chiefly cocci, that are capable of producing 

 superoxydases. According to Seligmann addition of an anti- 

 septic to milk in sufficient quantity to prevent bacterial growth 

 also decreases the amount of superoxydase, but when the anti- 

 septic is removed the quantity of enzym increases. This fact 

 points clearly to the bacterial origin of superoxydases. 



Catalase action is -inhibited by HCN, cyanids of potassium 

 and mercury, barium nitrate, hydrochloric acid, nitric acid, 

 hydrogen sulphid, acetic and oxalic acids, and potassium nitrate. 



Peroxydases or indirect oxydases have the property of produc- 

 ing colored compounds from easily oxidizable substances. When 

 fresh tincture of guaiac and hydrogen peroxid are added to milk, 

 a blue color appears. When old tincture of guaiac is used the 

 addition of hydrogen peroxid is not necessary, since a peroxid is 

 formed in the tincture. Similar color reactions are produced 

 with guaiacol, paraphenylendiamin, ursol D, dimethyl- and tetra- 

 methylphenylendiamin, paramidophenol, creasote, and other sub- 

 stances. Hydrogen peroxid must be present in these reactions. 



The reactions of peroxydases have been studied by Kastle and 

 Porch. . The authors found that the power of milk to induce 

 oxidation of leuko- compounds is intensified by certain sub- 

 stances of the phenol type. Phenolphthalein, guaiacum, and 

 paraphenylendiamin accelerate the reaction, and these substances 

 can be used with certainty as peroxydase reagents. Fresh milk 

 from different cows shows different peroxydase activity. They 

 have further shown that by means of the peroxydase reaction, 

 modified by addition of phenol accelerators, raw milk can be 

 distinguished from cooked milk, and raw milk from milk heated 

 to 70 C. or somewhat higher for short intervals. Milk heated 

 to 60 C. for twenty minutes increases the intensity of the reac- 

 tion slightly, while milk heated to 70 C. for one hour or to 75 C. 

 for twenty minutes no longer gives a peroxydase reaction. Per- 

 oxydase intensifies are trikresol, phenol, and beta-naphthol. 

 Most of the experiments were carried out with trikresol. One 

 c.c. of a 1 per cent, solution of trikresol was added to 5 c.c. of milk. 



The optimum temperature of peroxydases is 25 C., and they 

 are destroyed at 72 to 75 C. Prolonged heating at 70 C. is 



