FROM THE PRACTICAL VIEWPOINT 



loss of brine. Some heating tanks are now made 

 with double coils, one of which is used for heating 

 and the other for cooling. If the cooling is done^x 

 in tank pasteurizers there is the advantage that 

 the milk comes in contact with no additional metal 

 surface or other material after it is placed in the 

 tank till it is drawn into the final containers. 



The principal objection to the tank cooling is 

 that usually a long time is required to reach the 

 desired low temperature. As stated in the chap- 

 ter on heaters, the time is frequently from an hour 

 to an hour and a half. Large coils and a rapid 

 circulation of brine will decrease this cooling time 

 greatly. 



In country plants at a distance from the point 

 of milk consumption, the time of cooling is an im- 

 portant consideration from the dealers' point of 

 view, since the time between the receipt of the milk 

 from the farmer and the departure of the milk 

 train is limited. 



The change in temperature from the high heat 

 necessary to pasteurize the milk to the cold re- 

 quired for rapid cooling produces a considerable 

 strain upon the pipes of the coils, and the joints 

 are apt to become weakened. 



161 



