FROM THE PRACTICAL VIEWPOINT 



cooling the milk when it is made large enough to 

 take care of the milk which is to be treated. They 

 are made by various manufacturers in forms which 

 vary somewhat in details. Some are so arranged that 

 the regenerative principle is made use of. In most 

 of these the hot milk from the holder is allowed 

 to flow over pipes through which the incoming 

 cold milk flows. This is a means of saving heat 

 units, but such coolers are rather difficult to clean, 

 and there is a danger that the pressure of the cold 

 milk on the inside of the pipes will find openings 

 through which the milk will be forced into the pas- 

 teurized milk on the outside. The contamination 

 which results is not corrected by repasteurization. 

 Some one may say that the same danger exists when 

 the cooling medium on the inside of the pipes is 

 water. This is true, but it must be remembered 

 that the water pipes do not need to be taken apart 

 for cleaning, while the milk pipes must of neces- 

 sity be opened for cleaning daily, and the danger 

 from loosened joints is therefore greater. 



Another objection which has been urged to the 

 use of the open cooler is that the milk is exposed 

 to the air, and that there is great danger from 

 air contamination. This is true when the air is 



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