THE PASTEURIZATION OF MILK 



nau, and others have demonstrated the fact that 

 if milk is heated to a temperature of 140 F., and 

 is held at this temperature for twenty minutes, or 

 even less, all of the pathogenic or disease-produc- 

 ing bacteria will be destroyed. Also, if the milk 

 is heated to a uniform temperature of 158 F., 

 and held thereat for one minute, all such disease 

 germs will be killed. Between these extremes, dif- 

 ferent degrees of temperature, and correspond- 

 ingly varying lengths of holding time, will pro- 

 duce equally good results. These experiments 

 have been carried on of course in laboratories 

 where ideal conditions for securing accurate re- 

 sults existed. Accurate temperatures could be ob- 

 tained and the length of time for which the milk 

 was held could be carefully controlled. When, 

 however, pasteurization is carried on under com- 

 mercial conditions, where large quantities of milk 

 are handled, the same amount of accuracy is not 

 possible. There are variations in temperature and 

 variations in the length of time for which it is 

 held, due largely to the mechanical defects or 

 limitations in all forms of machinery. These fac- 

 tors of error render the results uncertain, and it 

 is therefore desirable that the temperatures and 

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