CHAPTER VI. 

 PRESERVATION OF MILK. 



It has been shown in a previous chapter that milk be- 

 comes contaminated with a multitude of bacteria not 

 only on the farm where it is produced, but during the 

 various stages prior to its use. Many of the bacteria 

 which find their way into milk are readily able to de- 

 velop, and by their growth, render the milk unfit, or 

 even harmful for human food. With the most stringent 

 precautions that can reasonably be taken, it is impossible 

 to avoid all contamination ; hence, all grades of milk will 

 soon spoil, unless some means of preservation is em- 

 ployed. Indeed, of all the foods classed as perishable, 

 milk is the one that most rapidly deteriorates. Pro- 

 duced under ordinary conditions, it is unfit for ordinary 

 use in a few hours if kept at 70 F. 



There are three possible ways by which milk may be 

 preserved : ( 1 ) The removal of bacteria that have gained 

 entrance to it; (2) The prevention of growth of the con- 

 tained bacteria; (3) The destruction of the contained 

 organisms. In practice at least two and sometimes all of 

 these methods are employed. The prevention of con- 

 tamination, a subject discussed in Chapter III is in 

 reality one of the most efficient means of preserving 

 milk. In milk production, as elsewhere, prevention is 

 preferable to cure. Milk produced under such condi- 

 tions that its germ content is but a few thousand per 

 cubic centimeter will keep much longer than that han- 

 dled in the ordinary manner. 

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