CHAPTER XV 

 PASTEURIZATION 



Definition. As applied to butter-making and city milk, pas- 

 teurization may be denned as a process of heating milk or cream 

 to a temperature sufficiently high to destroy the great majority 

 of the bacteria and other ferments contained therein and. cooling 

 it quickly to a low temperature. The name is derived from 

 Louis Pasteur, an eminent French scientist, who made the dis- 

 covery in the years 1860-64, that if wines were heated to a certain 

 temperature (70 C. or 158 F.), and cooled again, fermentation 

 would stop. 



In 1884 Soxhlet applied the method of heating to milk for 

 destroying bacteria. 



Storch Test for Pasteurization. S torch, at the Royal 

 Agricultural Experiment Station, Copenhagen, Denmark, was 

 the first to apply general pasteurization to cream for butter- 

 making. Denmark has a law making pasteurization com- 

 pulsory. This law was enacted to prevent the spread of tuber- 

 culosis among the herds. The law requires that milk or cream 

 must be heated to 80 C., or 176 F. Samples of skim-milk from 

 the creameries are required to be sent to the Experiment Station 

 where they are tested by tr^e Storch test to ascertain if creameries 

 are complying with the requirements of the law. 



Storch found that of all the reagents that might be used for 

 determining whether milk or cream had been heated to 80 C. or 

 176 ,., the best was paraphenylene diamine. This compound 

 ordinarily gives a brown color when acted upon by il active " 

 oxygen, but in the presence of casein in milk the color is a beau- 

 tiful indigo blue. 



To carry out the test about 5 c.c. of milk or cream are put 



201 



