CHAPTER VII. 

 PRINCIPLES OF MILK PRESERVATION. 



84. Keeping* quality. Where milk is consumed in 

 the form of milk or cream, it is desirable to retard or in- 

 hibit the fermentative changes as much as possible. In 

 the preceding chapters, the direct relation which exists 

 between the keeping quality of the milk and the germ 

 life of the same has been indicated, so that it is evident, 

 in order to perfectly preserve milk, the bacteria must 

 either be prevented from gaining an entrance, or de- 

 stroyed after they have once established themselves. 

 Bacteria are so widely distributed, and milk is such a 

 nutritious medium for their development, that to entirely 

 prevent their entrance and growth is not feasible. Scru- 

 pulous care in the dairy both before and after the milking, 

 will however, do much to reduce the germ content of 

 milk as is seen in the ' ' sanitary " or " certified ' ' milk 

 that is being put on the market in some cities. These 

 milks are drawn under the most careful conditions, and 

 then held during distribution in such a way as to retard 

 the course of the fermentative changes in a marked de- 

 gree. Milk so treated will remain sweet for several days, 

 which period is sufficiently long for practical purposes. 

 Such milk cannot well be produced in herds that are not 

 under one management as the degree of care necessary to 

 success is not often exercised unless under the direct su- 

 pervision of a competent manager. 



85. Preservation of milk. In considering methods 

 of milk preservation, reference will only be made to 



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