COOLING HOT-BOTTLED PASTEURIZED MILK. 
35 
arrangement the air was blown over steam coils and down through 
the crates, leaving the box near the bottom. The results are shown 
by means of curves in figure 20. In this case the crates were stacked 
five high, the pint bottles in the three lower crates, and the quarts 
in the two upper ones. By placing the quart bottles on top they 
came first into contact with the hottest air and naturally would be 
heated more quickly than the pint bottles at the bottom. There was 
still a wide difference in temperature, however, between the upper 
and lower tiers of bottles and also in the temperature of the top and 
bottom layers in the same bottle, where a maximum temperature 
difference of 82° F. (45.5° C.) was observed. It was therefore 
decided that neither of these methods is commercially practicable 
when the milk is contained in bottles. 
CURVE A/o.J- TEMPERATURE OUTGOING. AlfK. 
/Vo.2- » INCOMING. A/Ft. 
•• Ho. 3- - BOTTOM PT MIL. K. 
« Ho.**-. r. ., PTWATER. 
" /Vo.6- '< TOP QT WATER 
■> A/o. 7~ \t A7/1* DIEFEPENTI/Kl. 
" /Vo. <9- Iff TOP <?T MILK. 
so <?o &o <so 
T/MIE - MINUTES 
Fig. 20.— Heating by forced air.— Variation in temperature of bottles at different positions in stack. Hot 
air blown downward through crates. 
GENERAL SUMMARY. 
1. In these experiments bottles of water generally were used in 
place of milk, as it was found that there is very little difference in the 
relative rate of cooling milk and water. When quart bottles of milk 
and of water were cooled by forced-air circulation from 148° to 45° 
F. (64.4° to 7.2° C), the milk cooled more slowly, but the maximum 
difference was about 2° F. (1.1° C). On account of this small vari- 
ation it was considered advisable to use water, as it was more easily 
obtained and handled. Bottles of milk, however, were distributed 
throughout the crates for bacteriological studies as Well as for temper- 
ature readings. 
