CHAPTER VI. 

 STERILIZATION OF MILK. 



WE have seen in the preceding chapters that it is im- 

 possible to obtain a product of absolute keeping quality by 

 our common methods of handling the milk. It is well 

 known that the comparatively poor keeping qualities of the 

 milk cause great difficulties in its handling and sale, and 

 efforts were already long ago made to preserve the same so 

 that it could be better kept and more easily handled in the 

 trade. 



The simplest and most natural method of preserving 

 the milk has already been mentioned several times, viz., to 

 cool the milk sufficiently. It is hardly practicable in the 

 trade, however, as it is expensive and inconvenient con- 

 stantly to surround the milk with a cooling medium. This 

 is, nevertheless, the only way to preserve the milk without 

 its losing its original qualities; all other methods cause 

 greater or smaller changes in the chemical composition of 

 the milk, its taste, appearance, etc. 



Use of Chemicals. A method which has long been ap- 

 plied and as long been objected to, is to add all kinds of 

 antiseptics to the milk, salicylic acid, boracic acid, etc. ; 

 these substances partly kill the bacteria themselves and 

 partly prevent their growth; such milk is often sold as 

 " improved milk/' but ought properly to be called simply 

 adulterated milk. 



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