STORAGE OF FRUITS, VEGETABLES, AND FLORISTS' STOCKS 5 



of moisture on stored products, which in itself is undesirable because 

 it favors the growth of mold and the development of decay. 



Control of temperature is usually easier in large rooms than in 

 small ones if both are filled to capacity. This is because of the "fly- 

 wheel" effect produced by the larger mass of material, including 

 both the commodity and the building material. Refrigeration is thus 

 stored up, so to speak, and the temperature changes occur more slowly. 

 For this reason small storage rooms generally will require closer 

 attention than large ones. 



Humidity of Storage Rooms 



The relative humidity of the air in storage rooms has a direct 

 relation to the keeping quality of the products held in them. With 

 only a few exceptions (see especially onions), the most desirable con- 

 dition is that in which the humidity of the air in the storage room 

 is kept at approximately the moisture content of the produce stored 

 therein. If it is too low, wilting is likely to occur in most fruits, 

 vegetables, cut flowers, etc.; if it is too high, it favors the develop- 

 ment of decay, especially in rooms where there is considerable varia- 

 tion in temperature. The exact control of humidity is rather diffi- 

 cult, however, and in the past was not often attempted in commercial- 

 storage warehouses. However, at the present time new plants are 

 being designed and old ones changed over in such a way that a foun- 

 dation for humidity control in cold storage is being developed. 

 Sufficient refrigeration, whether coils or brine spray, is provided so 

 that the room can be operated with only a small difference in tem- 

 perature between the refrigerant and the air of the room, thus rais- 

 ing the dew point of the air and its relative humidity. This permits 

 the maintaining of high humidity. For low humidity the tempera- 

 ture of the refrigerant is lowered. To build up humidity quickly 

 in cold-storage rooms some operators evaporate water from insulated 

 open-top tanks equipped with insert electrical heaters. Others use 

 a fan to beat water into very fine particles and to blow this spray 

 into the room. These humidifiers are sometimes made automatic, 

 connecting with humidistats. However, if the coil temperature is 

 too low, that is, if the spread between the temperature of the refrig- 

 erant and that of the room is too great, the effect of these various 

 measures will be short-lived. The relative humidity will soon become 

 undesirably low, and harmful drying out of the stored product will 

 occur. 



When warm products are placed in a cold room the spread between 

 commodity temperature and refrigeration temperature is wide at 

 first. Such a condition hastens cooling and shortens the time during 

 which undesirable changes can occur in the commodity. As the 

 spread is reduced, the cooling proceeds more and more slowly. 

 Eventually, if the temperature of the refrigerant is properly adjusted 

 and there is adequate refrigerated surface, the desired temperature 

 can be reached without subjecting the commodity to excessive desic- 

 cation. If it could be successfully managed under commercial con- 

 ditions, a temporary reduction in refrigerant temperature below what 

 is desired or safe for long-time operation would be extremely helpful 

 in shortening the initial cooling period. 



