ENZYMS IN MILK 239 



All the above tests depend on the presence of peroxydases in 

 milk. 



Schardinger' s Test. — This test depends upon the decolorizing 

 action of a reductase in milk. The original test devised by Schard- 

 inger was made with methylene-blue, but later a small amount of 

 formalin was added which rendered the test more sensitive. The 

 reagent is composed of 5 c.c. of a saturated alcoholic solution of 

 methylene-blue, 5 c.c. of formalin, and 190 c.c. of water. To 1 c.c. 

 of this reagent 20 c.c. of the milk are added. The mixture is im- 

 mediately covered with a layer of melted paraffin or paraffin oil 

 to exclude the oxygen of the air. The tube is placed in a water- 

 bath at 45° C. If the milk was heated above 72° C. the color 

 disappears. The reductase is destroyed at somewhat lower tem- 

 perature than the peroxydase, and this test, therefore, has a larger 

 range of temperature than tests depending on peroxydase reactions. 

 If the tube is kept at 37° C. instead of 45° C. a negative result is 

 obtained if the milk was heated for five minutes at 65° C. Below 

 65° C. the reaction is doubtful. Decolorization may be partial, 

 but whether such partial decolorization can be used as an indica- 

 tion of heating has not been definitely determined. 



BIBLIOGRAPHY 



Babcock and Russell: Univ. of Wis. Agri. Exper. Sta., 14th Annual Report, 



1897, p. 161. 

 Babcock, Russell, and Vivian: Univ. of Wis. Agri. Exper. Sta., 16th Annual 



Report, 1899, p. 175. 

 Babcock, Russell, Vivian, and Hastings: Univ. of Wis. Agri. Exper. Sta., 



16th Annual Report, 1899, p. 157. 

 Bauer: Die Methodik der Biologischen Milch Untersuchung, Stuttgart, 



Ferdinand Enke, 1913. 

 Harding and Van Slyke: New York Agri. Exper. Sta., Technical Bull. 6, 



December 1907. 

 Kastle and Porch: Jour, of Biol. Chem., 1908, vol. 4, p. 301. 

 Rogers: Cent. f. Bakt., Abt. 2, 1904, vol. 12, pp. 388, 597. 

 Seligmann: In Sommerfeld's Handbuch der Milchkunde. 

 Spolverini: In Sommerfeld's Handbuch der Milchkunde. 

 Van Slyke: Modern Methods of Testing Milk and Milk Products, New York, 



Orange Judd Company, 1915. 



