PASTEURIZING MILK. 
17 
cool air against the bottle, heat would constantly be given up with 
more rapidity by the milk and the cooling process hastened. In figure 
8 are shown the temperatures in three bottles of milk cooled for 30 
minutes in air. One bottle was cooled in still air at 77° F., one was 
cooled in an air blast from an electric fan at a temperature of 77° F., 
and one was cooled in still air at 35° F. At the beginning of the 
cooling the temperature of the milk was about 145° F. As will be 
seen from the curves, after 30 minutes' cooling the temperature of the 
milk in the bottle cooled in still air at 77° F. was about 127.5° F., 
while that of the milk cooled in an air blast at 77° F. was about 
102° F. It is noted that by cooling in an air blast for 30 minutes 
iSO°F. 
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Cooling period in minutes. 
Fig. 8. — Effect of cooling a quart bottle of milk in still air and in an air blast. 
there was a reduction in temperature of about 25.5° F. in excess of 
that obtained under the same conditions in still air. The temperature 
curve of the milk in the bottle cooled in still air at 35° F. follows 
closely that of the milk cooled in still air at 77° F. It is also inter- 
esting to note that after cooling for 30 minutes in still air at 35° F. 
the temperature was 122° F., while that of the milk cooled in an air 
blast at 77° F. was about 102° F., a difference of 20° F. 
Since these experiments indicated that hot bottled milk might be 
cooled more rapidly by using a blast of cold air, another experiment 
was conducted in which one quart and one pint bottle were cooled in 
still air which averaged 39.4° F. and another set in an air blast the 
temperature of which averaged 44.3° F. The blast of cold air was 
obtained by placing an electric fan in a refrigerator. The fan de- 
