CHAPTER IX. 

 GENERAL POINTERS. 



1. Sterilization in the scientific sense means the absolute kill- 

 ing of all germs and requires a temperature of 230 and one which 

 spoils milk for commercial and manufacturing purposes. 



When used about milk, it means its heating to from 210 to 218 

 Fahr. under pressure and holding it for not less than 30 minutes and 

 then cooling to 50 or thereabout. 



2. Intermittent Sterilization means the above process repeated 

 having the milk warm sufficient time to develop the germs between 

 the operations. 



3. Pasteurizing means heating to between 150 and 160 Fahr. 

 and keeping it there for 20 or 30 minutes then cooling it to 50 or 

 thereabout. 



4. Heating alone is not pasteurizing, but the term is also used 

 when the milk or cream is simply heated and cooled immediately 

 which is sufficient for cream which is to be ripened. 



5. The keeping of the high temperature for 20 or 30 minutes is 

 absolutely essential if the milk or cream is intended for commercial 

 purposes. 



6. Intermittent Pasteurizing will prolong the keeping quality 

 of the milk considerably. 



7. The effectiveness of pasteurization (and sterilization) is in 

 proportion to the height of the temperature and the length at which 

 the material is exposed to it. Thus heating at a lower temperature 

 for a longer time may be as effective as a higher temperature for a 

 shorter time. 



A lower temperature than 150 Fahr. is considered useless. 



8. Pasteurizing is but of little avail unless all cans, bottles and 

 utensils are sterilized. 



9. Pasteurizing is of the more value the nearer to the milking 

 time it is brought; there will be fewer bacteria to kill. 



10. The quickest heating effect and the least "scorching" of the 

 milk is obtained when the milk is kept in constant motion by flowing 

 over the heating surface (not too slow) or by a stirrer as in the Fjord 

 or the Russell or the Boyd apparatus. 



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