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 Sommerf eld's Handbuch der Milchkunde. 

 Spolverini: In Sommerf eld's Handbuch der Milchkunde. 

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



Orange Judd Company, 1915. 



