CHAPTER VIT 

 PASTEURIZATION 



Pasteurization is the process of heating a Hquid to such 

 a temperature and for such a period of time that nearly 

 all the micro-organisms in it are killed. It also includes 

 the subsequent rapid cooling of the liquid. 



68. History. — Pasteurization was developed by Louis 

 Pasteur, from whom it derives its name. In the years 

 1860 to 1864 ^ this eminent scientist discovered that wine 

 fermentation is due to micro-organisms, and he found 

 that if the wine were heated to a certain temperature and 

 cooled again, the fermentation stopped. In 1886 Soxhlet ' 

 applied this method of destroying bacteria to milk and to 

 certain milk products. Pasteurization is not sterilization, 

 as shown in Chapter XVI . Nevertheless, efficient pasteur- 

 ization will kill at least 99.9 per cent of the micro- 

 organisms. 



Pasteurization was first accomplished by the " holder " 

 method. In this system all the milk or cream was heated 

 at one time in a receptacle, and held for a definite period 

 at a certain temperature, then it was cooled. Russell ^ 

 was one of the first to study the application of pasteur- 

 ization to commercial dairying. He began his studies 



' Rosenau, M. J., Pasteurization. U. S. Hygienic Labora- 

 tory, Bui. 41, p. 591, 1908. 



2 Russell, H. L., Pasteurization of Milk and Cream for Direct 

 Consumption, Wis. Exp. Sta., Bui. 44, 1895. 



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