18 
BULLETIX 240, U. S. DEPARTMENT OF AGRICULTURE. 
livered air at a velocity of about 1.250 feet per minute. The tem- 
perature curves in figure 9 show the results of this experiment. The 
temperatures of the hot milk at the beginning of the cooling ranged 
from 110° to about 113.5° F. in the different bottles. It will be seen 
from the curves that five and one-half hours were required for the 
temperature of the quart bottle of milk in still air to reach 50° F., 
while the milk in a quart bottle in an air blast was cooled to 50° F. in 
a little over two hours. The milk in the pint bottle cooled in still air 
reached a temperature of 50° F. after about three and one-half hours, 
while only one and one-half hours were required to cool the milk 
in the pint bottle which was in a blast of cold air. 
From these results there can be no doubt as to the value of an air 
blast for cooling bottles of hot milk, at least as compared with still 
air as a cooling medium. As these experiments were made on single 
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120° F. 
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7o°F. 
6o°F. 
50 F. 
4 o°F. 
Fig. 9.- 
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Cooling period in hours. 
-The cooling of pint and quart bottles of hot milk in still air and in an air blast at 
refrigerator temperature. 
bottles it was thought advisable to try cooling several crates of 
bottled hot milk by an air blast. Specially constructed skeleton- 
frame steel crates were used, so as to allow a free circulation of air. 1 
Milk was pasteurized at 115° F. for 30 minutes and bottled hot in 
ordinary milk bottles by the aid of a hand bottle filler. The bottles 
were then capped with the ordinary cardboard caps and placed in 
crates. Four crates were used in these experiments, two filled with 
quart and two with pint bottles. The two crates which contained 
quart bottles were placed in a refrigerator room one above the other, 
and directly back of them were placed the two crates of pint bottles 
one above the other. The air blast was Generated bv a 16-inch desk 
Mr. John T. Bowen. of this division, assisted in this work. 
