ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 243 



^while that from the next is being drawn. This is good for the 

 milk, and it saves a tiresome delay of waiting for it to cool 

 after all the milking is completed. It is not sufficient to set a 

 can in a cold place and allow it to cool slowly; this requires 

 several hours and gives time for the germination of spores and 

 the development of bacteria. In order to get full advantage of 

 low temperature the cooling must be completed at the earliest 

 possible moment, and it should be carried down to about 40 

 degrees F. At temperatures above 40 degrees F. and below 60 

 degrees F. some species of bacteria thrive, though they do not 

 cause as much trouble or loss as those which grow at still higher 

 degrees. Milk from dairies where cooling is not practiced is 

 frequently sour or tainted when it arrives at the factory; in such 

 cases cooling is a preventative needed, and the labor necessary 

 will be well repaid by the better product. 



A common way of cooling is to place the can in a trough or 

 vat of water and stir the milk; this is a tiresome operation, and 

 the work is liable to be slighted; if the can is only half filled the 

 temperature falls faster than when it is full. Putting ice into 

 milk or cream must be done with caution; water is thus added, 

 and there is danger besides of adding many impurities and germs 

 which are not destroyed by freezing. 



Cooling is so closely connected with aerating that the terms 

 are often confused. Machines are constructed for the double 

 purpose of performing both these operations at the same time. 

 These are more efficient than setting in water and occasionally 

 stirring by hand, and they are not very expensive. Milk may 

 be cooled by such contrivances from 30 to 40 degrees in a few 

 minutes. Coolers have have a current of water running through 

 them at the same time milk is running over the outside, cool the 

 milk to within 3 or 4 degrees of the temperature of the water; 

 such thorough work requires several times as much water as the 

 bulk of milk. The best results are obtained when the cool- 

 ing agent enters the cooler at the bottom and leaves at the top, 

 so the milk is partly cooled before it receives the effect of the 

 coldest water. Where running water is not available, a form of 



