COOLING HOT-BOTTLED PASTEURIZED MILK. 



35 



arrangement the air was blown over steam coils and clown 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 

 stm 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° Y. (45.5° C.) was observed. It was therefore 

 decided that neither of these methods is commercially, practicable 

 when the milk is contained in bottles. 



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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 cooh^d 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 casUy 

 obtained and handled. Bottl(^s of milk, however, were distributed 

 throughout the crates for bacteriological studies as well as for temper- 

 ature readings. 



