HOME FREEZING 11 



occurring in food stored at 10°. The foods stored under the above conditions 

 were definitely inferior in quality to those stored at 0°. It was suggested that 

 exposure of frozen foods to temperatures above 0° rather than merely tempera- 

 ture fluctuation may be a major factor influencing deterioration of food quality. 

 These results further emphasize the importance of maintaining storage tempera- 

 tures in home and locker freezers at 0°F. or below. 



What About Power Failure or Freezer Breakdown? 



It is important that all home freezing cabinets be equipped with some sort of 

 an alarm or warning system that will indicate when the temperature inside of 

 the cabinet gets too high owing to power failure or mechanical breakdown. Al- 

 though such failures may be uncommon, the individual may lose considerable 

 quantities of food if adequate precautions are not taken. It has been reported 

 that food in a loaded freezing cabinet will remain frozen for from two to five days 

 depending upon the size of the cabinet, size of load, etc. (U.S.D.A., 19; Tressler, 

 Evers and Long, 16). 



In order to obtain further information on temperature changes that take place 

 in a home freezer when the power is shut off, some experimental tests were made 

 using a 12.5-cubic-foot cabinet. The side walls and bottom of the cabinet con- 

 tained five inches of moisture-proof, low-density, insulation. The two covers 

 on top contained three inches of the above insulation. The hinged covers made 

 a tight seal on rubber gaskets and were held tightly closed by means of an adjust- 

 able latch. Each of the two compartments of the cabinet had separate covers 

 and each was divided in half on the inside providing four sections, one of which 

 was a freezing section. 



Temperature changes inside the freezing cabinet during the tests were fol- 

 lowed by means of twelve iron-constantan thermocouples connected to a Leeds 

 and Northrup "Micromax" automatic recording potentiometer with stations for 

 twelve thermocouples. All four sections of the freezer cabinet were filled with 

 packages of frozen apples. Thermocouples were placed in the centers of six 

 packages of fruit which were placed in various parts of the cabinet. Other 

 thermocouples were placed in the bottom and top in each of the two compart- 

 ments. After the freezer had been operated 24 hours to reach equilibrium, it 

 was shut off and the temperatures at the different points were recorded con- 

 tinuously for eight days. At the end of this time the food was removed from 

 the freezer. All of it had thawed completely, but there was no evidence of bac- 

 teriological spoilage. The products were in good condition as evidenced by their 

 color and flavor. 



The data are presented in figure 1. These show the average rise in tempera- 

 ture at the bottom and top of the freezer and in the packages of food. The 

 temperature in the cabinet rose rapidly up to 30°F. during the first two days 

 but there was a rise of only iwo degrees from the third to the sixth day and a rise 

 to 40°F. by the end of the eighth day. The temperature in the packages of food 

 lagged behind that of the cabinet. 



The results of a similar experiment to determine the effect of a power shut-off 

 when the freezer was one-half full of frozen food are summarized in figure 2. 

 This test was set up in the same manner as described above with the exception 

 that only two sections of the freezer were filled with frozen food. At the end of 

 five days the food was removed from the freezer. It was completely thawed but 

 showed no evidence of spoilage. With the freezing cabinet only one-half full the 

 rise in temperature was much more rapid than when the unit was completely 

 filled. 



