FROM THE PRACTICAL VIEWPOINT 



In fact, any straining after the milk leaves the 

 holding apparatus is undesirable, and seems to be 

 useless if the milk has been well cleaned before 

 pasteurizing. 



Coolers 



The rapid cooling of heated milk has been held 

 to be an important factor in the satisfactory pas- 

 teurizing of milk. It was claimed that the sud- 

 den chilling had a destructive effect upon the bac- 

 teria, which had been already weakened by the 

 heating. Investigations made by Ayers and John- 

 son, however, seem to indicate that when the cool- 

 ing is accomplished, during a period of two hours, 

 there is no noticeable increase in bacterial growth. 



There are three general types of milk coolers 

 in use: 



First: The open cooler or aerator. This consists 

 of a series of tubes, made usually of copper and 

 well tinned. These tubes are arranged one above 

 another, and are so connected at the ends that cold 

 water or brine is forced through the entire series. 

 The water flow is into the lower tubes and up- 

 ward through the series, so that the coldest water 

 comes in contact with the coldest milk. This form 

 155 



