PACKAGED ICE CREAM 



201 



assumed specific heat of 0.5 calories per gram. The approximate theo- 

 retical rise in temperature of a 10-ounce quantity of ice cream would be 

 about 3.6° F. or enough to melt about 5 grams of ice. However, because 

 of the extremely slow conductivity of a semi-frozen ice cream, only a thin 

 layer next to tlie carton is aflfected. It is probable that this melted film 

 is the cause of a slight shrinkage that is experienced in packaging a given 

 lot of ice cream from the freezer. Although this. film of melted cream 

 would be expected to form an icy outside layer, it is not noticed by the 

 consumer because it is the first to melt. The slow rate of heat transfer 

 which takes place in a pint size package is shown in Figure 2, made from 

 temperature readings taken from the inner side of the carton and at the 

 center of pint samples drawn at the temperatures shown by the first 

 center temperature readings. 



Fig. 



The Rate of Cooling of Pint Packages of Ice Cream in the Hardening Boom 

 at 4." r. 



20 





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From this same graph it will be noted that more than one hour was 

 required for the cold to reach the center of the pint package. This very 

 long cooling period also points very strongly to the conclusion that the 



