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Table 1. Vapor pressure deficits at various temperatures and humidities, 



Relative 

 humidity 



32 



HI 



Temperature C°F) 



50 



68 



100 

 95 

 90 

 80 

 70 

 60 

 50 



Vapor pressure deficit (mm mercury) 



The importance of moisture loss is obvious when fruits begin to shriv- 

 el. Their salability is rapidly lost. However, moisture loss can be 

 significant even though shrivelling has not developed, because a fruit 

 usually loses about 5% of its weight before any shrivelling occurs. This 



means that when fruits show traces of shrivelling, 5% of their weight 



and 5% of your income have literally evaporated. Conscientious main- 

 tenance of humidity, and reduction of moisture loss, will save you money . 



Every storage should have a humidity gauge in it, and it should be 

 read frequently. If RH falls below 90-95%, the room should be humidified, 

 with care taken that RH does not greatly exceed 95%. Golden Delicious 

 should always be stored in unsealed polyethylene bags, since they are ex- 

 ceptionally subject to moisture loss due to a poor wax covering on the 

 skin. And, particular attention should be given to humidity control fol- 

 lowing storage when the fruits are at a higher temperature, because mois- 

 ture is being lost rapidly. 



If you are packing fruit in perforated polyethylene bags following 

 storage, you need not worry about excessive moisture loss after storage, 

 for humidity will almost always be near 100% in these bags. The problem 

 under these conditions will be to prevent condensation of moisture in 

 the bags, which will then stimulate fungal growth and subsequent fruit 

 decay. Condensation will very quickly occur if warm packages are placed 

 into cold storage. 



Thus, we are back to our 2 -pronged problem: to maintain humidity 

 high enough to keep moisture loss at a minimum, yet low enough to reduce 

 decay. This problem is important to anyone handling fresh fruits and 

 vegetables, and it should be well understood. 



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