HOME REFRIGERATION 11 



corresponding positions in the two refrigerators. Fresh tomatoes and radishes 

 were sliced as for use in a salad and stored as left-overs. 



The refrigerators were set at their normal operating positions and their mean 

 temperatures varied between 39°F. and 42°F. throughout the tests. The tempera- 

 tures of the refrigerators themselves varied one from the other by only about l^F. 



Ordinary refrigerator dishes with loose fitting glass covers and small custard 

 dishes with oiled silk covers were used as containers. The humidity in both 

 types of covered dishes was 100 percent. The dishes were used both covered 

 and uncovered so that a wide range of storage humidities (from 42 to 100 per- 

 cent) was obtained. Thus it Was possible to determine the effect of humidity on 

 the keeping quality of the foods. 



Ordinary household conditions of load and door openings were approximated 

 in most cases but these conditions were varied in order to obtain different relative 

 humidities in the boxes. 



Several samples were prepared for each test condition so that a complete sample 

 was available each day for analysis. 



The tests were run for at least four days and samples removed periodically to 

 determine the change in quality. The tests for quality consisted of determinations 

 of the loss in weight, vitamin. C content, moisture content, change in pH value, 

 and organoleptic tests. 



Approximately 25-gram samples were used for the ascorbic acid determina- 

 tions. At first representative samples were taken directly from the stored foods 

 but later it was found advisable to grind the whole storage sample and then sample 

 the ground-up material for the ascorbic acid determination. 



On account of the possibility of dehydration during storage especially at the 

 lower humidities, the ascorbic acid content is reported on a dry weight basis. 



Change in pH Value During Storage 



In no instance diil the pH value of any of the foods show a significant change. 

 The maxinium change in four days storage was only 0.4 pH units. No variation 

 in pH value could be attributed to the differences in humidity. 



From these results it was evident that the pH value could not be used as an 

 indicator of spoilage or aufolytic changes in foods stored in a refrigerator under 

 these conditions. ' 



Effect of Humidity on the Loss of Weight During Storage 



The percentage loss of weight of the various foods at the different storage 

 humidities for several tests is summarized in table 4. For any one vegetable the 

 same size sample was used and stored in similar containers. As the humidity 

 was reduced from 100 percent there was a progressive loss of weight, due to the 

 evaporation of water. This loss amounted to as much as 15 to 28 percent in four 

 days at the lower humidities, even in the case of mashed potatoes and fresh vege- 

 tables stored without juice such as radishes and sliced tomatoes. 



At humidities above 75 percent the loss of weight was 10 percent or less. At 

 100 percent relative humidity the loss in weight was only about 1 percent. It 

 should be noted that the loss of moisture appears to be a direct linear function 

 of the time and depends on the relative humidity. 



