chai'11':k XV 



PASTEURIZATION 



Definition. — As applied to butter-making and city ]iiill<, jtas- 

 teurization ma}' be deruied as a i)rocess ul heating milk ur cream 

 to a temperature suthcienth" high in destmy the great majurit}' 

 of the bacteria and other ferments contained therein and cuoling 

 it quickh' to a low temperature. The name is derix'ed from 

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

 covery in the }'ears 1860-64, fh^t if wines were heated to a certain 

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

 would stop. 



In 1884 Soxhlet a]>i)lied the method of heating to milk for 

 destro}ing bacteria. 



Storch Test for Pasteurization.- Storch, at the Iio\-al 

 Agricultural Experiment Station, Cojienhagen, Denmark, was 

 the first to apply general pasteurization to cream for butter- 

 making. Denmark has a law making pasteurizatioir com- 

 pulsory. Tliis law was enacted to i)re\-ent the spread of tulier- 

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

 must be heated to So° C, or 176^^' F. Samples of skim-milk fmm 

 the creameries are required to be sent to the Experiment Station 

 w'here they are tested by the Storch test to ascertain if creameries 

 are compl}-ing 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 heate<l to 80" C. or 

 176° F., the best was paraphen}dene diamine. This compound 

 ordinarily gives a brown color when acted ujjon b}" " actiA e " 

 oxv"-en, 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 



