BACTERIOLOGY OF MILK 455 



Uninspected Milk.— Even yet in the United States most 

 milk which is sold to the consumer is uninspected and no 

 sanitary control whatever is maintained. In a few instances, 

 cities have established maximum standards for bacterial 

 count, and withdraw licenses from those who sell milk con- 

 taining more than the maximum number of organisms. 

 Such ordinances, however, are difficult to enforce. 



Pasteurized Milk — Pasteurization has already been 

 defined as heating milk for such a time and temperature 

 as will destroy any disease-producing bacteria present and 

 not seriously injure the flavor or creaming qualities of the 

 milk. In some cases, the term "pasteurized" has been used 

 to indicate a milk of supposedly superior quality that has 

 not been actually heated. This, of course, is misbranding. 

 Pasteurization is a technical operation, requiring some 

 intelligence on the part of those carrying out the process. 

 In some instances the label "Pasteurized" has been used to 

 mean that milk has passed through an apparatus called a 

 "pasteurizer" whose efficiency is wholly unknown. 



Pasteurization may be carried out in the home. It is best 

 then to heat the milk in stoppered bottles to 60° c, hold at 

 this temperature for at least 30 minutes and cool rapidly. 

 In commercial pasteurization, two types of pasteurizers are 

 used. In the so-called flash process, the milk is heated to 

 the required temperature, usually 80° to 85° c, and main- 

 tained at that temperature for from 30 seconds to a minute. 

 It is then cooled and maintained at a low temperature until 

 distributed. In the holder process, the milk is kept at a 

 temperature required, 60° to 65° c, for about half an hour. 

 A combination of the two methods ie particularly efficient. 

 Usually over 99 per cent of the bacteria present in milk can 

 be destroyed by proper pasteurization. All pathogenic 

 microorganisms should be destroyed. 



