530 MICROBIOLOGY OF FOODS 



PASTEURIZATION 



ECONOMIC CONSIDERATIONS. In the preservation of food by heat, 

 two processes are applicable, pasteurization and processing or steriliz- 

 ation. In pasteurization, the aim is not to effect the permanent 

 preservation of foods or drinks by destroying all life present, but 

 rather to destroy certain species of organisms, thus checking the 

 natural fermentation, and effecting a temporary preservation. 



The principle of pasteurization may be said to have originated in 

 the early work of Spallanzani and Scheele, already mentioned, and 

 was employed by Appert in his later investigations. The operation 

 as carried out by Appert does not, however, appear to have found 

 general application until Pasteur revived the method, and as a result 

 of his activities in attempting to secure a general adoption of the 

 practice to prevent the spoiling of wine, the process was named from 

 him. 



SPECIFIC APPLICATION. Beer. Pasteurization is of economic im- 

 portance particularly in the dairy and fermentation industries, and 

 has perhaps had its widest application in the brewing industry. The 

 method as stated by the Schlitz Brewing Company is as follows: 

 " The process of pasteurization is in use with even the smallest brewers 

 in the United States, beer being pasteurized even for local consumption. 

 The beer is pasteurized in bottles by being subjected to a temperature 

 of 58 to 63 for one-half hour. The entire process as practised in the 

 large breweries requires less than an hour, and includes the warming of 

 the cold bottles to pasteurizing temperature, the pasteurizing proper, 

 and the cooling down to a little above room temperature. The process 

 is a continuous one, the bottles being put into the machine at one end 

 and taken out at the other." 



Fruit Juices. The essentials in the pasteurization of wine and fruit 

 juices are similar to those for beer. There is^ however, no universal 

 rule of application. Details of the process must be worked out to suit 

 the character of the different liquids under treatment. 



Cream and Milk. Pasteurization as employed in the dairy industry 

 varies in its method of application according to the purpose for which 

 it is used. Milk or cream as ordinarily received at creameries contains 

 a widely variant microbial flora, many of the species exerting a greater 

 or lesser influence in determining the flavor of the finished product. 



