THE PASTEURIZATION OF MILK 



Whatever form of tank holder is used, it is nec- 

 essary that it be thoroughly sterilized before use 

 each day, by the admission of live steam for a 

 considerable period of time. This sterilization is 

 of importance not alone for the destruction of the 

 bacteria contained in it, but also in order that the 

 pipes and tanks may become thoroughly heated im- 

 mediately before use. If they are not so heated, 

 it will be found that the milk first admitted to the 

 apparatus will be considerably cooled, and will be 

 discharged at a temperature much below that re- 

 quired by the regulations, and will so continue until 

 the hot milk has itself slowly heated the appa- 

 ratus. This may require fifteen or twenty minutes. 

 It will be found under such circumstances that the 

 milk first discharged from a holder contains many 

 more bacteria than that which flows from it after 

 the machine is heated. 



Another form of holder which belongs to the ab- 

 solute type is that which is represented by the tank 

 heaters shown in Figs. 11, 12, 13, 14, 14-B, 15, 16, 

 and previously described. In these the milk, after 

 having been heated, is allowed to remain for any 

 desired length of time, and is then released. This 

 method of holding has produced very satisfactory 

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