38 BULLETIN 420, U. S. DEPARTMENT OF AGRICULTURE. 
at a temperature of, say, 60° or even 70° F. (15.5° to 21.1° C.) may 
be used to cool the milk partly, the remainder of the cooling being 
done by mechanical refrigeration. It should be noted, however, 
that in cooling milk on a large scale by this method some unforeseen 
difficulties may arise which we did not encounter in our experiments. 
This process of cooling by forced-air circulation, if commercially 
practicable, could be applied to advantage for cooling hot-bottled 
pasteurized milk. Briefly stated, the complete pasteurizing and 
cooling process could then be as follows : 
Milk could be pasteurized by the ordinary holder system at 145° F. 
for 30 minutes. It could then be bottled hot in special oversized 
milk bottles of the ordinary type and capped with ordinary sterile 
caps. Before being filled, the bottles could be steamed for two 
minutes by running the crates inverted on a conveyer over steam 
jets; the bottles would then go through the bottling machine in a 
hot condition and would be practically sterile. The crates of hot- 
bottled pasteurized milk could then be cooled by stacking in a 
refrigerator room and blowing cold air through the crates. In the 
cold season outside air could be used for cooling, and in the warm 
season refrigerated air could be circulated through the crates. 
This process could be modified in two ways: The hot milk could 
be held in the bottles at 145° F. instead of in a tank, and the crates 
of hot pasteurized milk could be cooled by spraying with cold water 
instead of air. 
From a sanitary point of view the important advantage of the 
process of bottling hot pasteurized milk in hot bottles lies in the fact 
that bottle infection is ehminated, and if the bottles of hot milk can 
be cooled successfully by forced-air circulation, the process of pas- 
teurization would be raised to its highest state of efficiency by 
relatively simple methods. 
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