PASTEURIZING MILK. 



19 



fan, which gave an air velocity of about 1,250 feet per minute. The 

 fan was placed about 2^ feet in front of the pile of four crates 

 directly facing the crates with quart bottles. Temperatures were 

 taken in two quart bottles, one in the front and the other in the back 

 row. In this experiment the crates were cooled in a refrigerator 

 room, the temperature of which varied from 40° to 44° F. The 

 results of this experiment are shown in figure 10, together with the 

 results of a similar experiment in which the crates were cooled in an 

 air blast at a temperature of about 76° F. for a period of 2| hours. 

 The crates were then placed in a refrigerator and the cooling con- 

 tinued, a blast of air with a temperature of about 41° F. being used* 

 The curves in figure 10 show the averaged temperatures of two quart 



140 F. 



13°° F. 



no°F. 



100° F. 



















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8o°F. 

 7o°F. 

 6o"F. 

 50° F. 

 40° F. 



3o°F. 



O IS 3° 45 1 hr. 15 30 45 2 hrs. 15 30 45 3 hrs. 15 30 45 4 hrs. 15 



Cooling period. 



Fig. 10. — Effect of cooling crates of bottled hot milk in an air blast at different 



temperatures. 



bottles. It will be seen from curve A that about 3 hours and 7 min- 

 utes were required to cool the milk in quart bottles from 140° to 

 50° F. when cooled in a blast of cold air during the entire period. 

 A comparison of curves A and B shows that it took only about 45 

 minutes longer to cool to 50° F. the milk in bottles exposed to an air 

 blast at room temperature for the first 2^ hours. It is interesting to 

 note that curves A and B follow each other fairly closely during the 

 first 30 minutes of cooling. These results suggest that the cooling of 

 hot pasteurized bottled milk may be accomplished by cooling with an 

 air blast at ordinary room temperature and completed by cooling in 

 a blast of cold air in a refrigerator room. The greater the number of 



