REFRIGERATION IN THE DAIRY 695 



conical capillary cooler, called the " primary " cooler, in which 

 the ordinary water supply circulates. Here the milk is 

 reduced to a temperature approximating to the normal 

 temperature of the water, and is passed over a "secondary" 

 cooler in which brine circulates at the temperature of about 

 35 F. The milk leaving the secondary cooler will test about 

 38 F. and, so far as our knowledge at present goes, it will be 

 germ-free. Another method is to put the milk in bottles 

 and place it in what is inaccurately termed a " steriliser." The 

 steriliser is maintained for twenty minutes at a temperature 

 of 140 F., and the heat has the effect of killing the mature 

 organisms present, but not the undeveloped germs. Cooling 

 is as necessary in this as in the other case, and the bottles are 

 at once removed and placed first in a tank of running water, 

 and afterwards in a cold store held at 38 F. 



In Cheese-making 1 , the use of the refrigerating machine is 

 revolutionising the practice. It has, for example, been shown 

 that in ripening Cheddar cheese, a better product results 

 when the temperature is controlled than when it is left to 

 chance. It is held by some authorities that curing at a 

 temperature of 40 F. gives an infinitely better result than 

 can be attained at higher temperatures, the loss being reduced 

 to a minimum, the flavour perfect, and the production of 

 deleterious moulds held in check. So, in the treatment of 

 other classes of cheese, it is being gradually realised that the 

 control of the temperature is essential to the profitable con- 

 duct of the business. The whole subject is at present hardly 

 beyond the initial stages of experiment, but it may be 

 assumed, however, that in the future much attention will be 

 given to it. In Canada, from whence we receive three-fourths 

 of the cheese we consume, experiments have been recorded, 

 and many are now in progress, which it is believed will throw 

 much light on the question. 



The following definition of refrigeration 1 will add interest 

 to the subject, which has hitherto been treated from the 

 practical side : 



When a solid body is converted into a liquid, or a liquid 



into a gas or vapour, the change of state is accomplished in 



each case by the absorption of heat. While the change is 



going on the temperature of the body does not rise, and the 



1 From Refrigeration in the Dairy, by Loudon M. Douglas. 



