COMMERCIAL STORAGE OF FRUITS AND VEGETABLES 6 



tare in storage rooms be held fairly constant. Variations of 2 or 3 

 degrees above or below the desired temperature are in most cases 

 too large. They can usually be avoided if the storage rooms are 

 well insulated throughout and are furnished with adequate refrigera- 

 tion and equipped either with reliable, accurate thermostats or with 

 means for manual control which are given frequent personal atten- 

 tion by some one charged with that duty. Even when reliable auto- 

 matic controls are used, frequent personal visits to storage rooms 

 should be made. 



In commercial cold-storage rooms thermometers are usually placed 

 at about the level of the eyes of a man of ordinary height, sometimes 

 slightly lower. It is important however to take temperatures fre- 

 quently at the floor and the ceiling also, or at any other places where 

 they might be expected to be undesirably high or low. If the air 

 in certain locations seems always to be too warm or too cold it may 

 be necessary to install fans to increase the rate of air movement and 

 so bring about a better equalization of the temperature in various 

 parts of the room. 



Most varieties of apples keep best and longest if held constantly 

 at 31.5° to 32° F. ; the best temperature for Bartlett pears is be- 

 tween 30° and 31°. If the air temperature where either of these 

 fruits is stored rises 2 or 3 degrees above the upper limit mentioned, 

 there is danger of increased decay and undue ripening, the danger 

 being greater the longer the period during which the temperature 

 is above 32°. For example, 3 or 4 days at 35° usually would have 

 little or no effect, partly because of a slower rise in the temperature 

 of the fruit than in that of the air; but 10 days at this temperature 

 would probably shorten the life of the fruit by about a week and 

 possibly result in more decay. On the other hand, if the tempera- 

 ture goes a degree or two below 30°, there is a chance that freezing 

 will occur. Celery and cabbage allowed to remain too warm in 

 storage may show yellowing and decay ; potatoes are likely to begin 

 to sprout if the temperature is too high and usually become unde- 

 sirably sweet if it is too low. Other commodities undergo these or 

 other kinds of deterioration if the temperature variations through- 

 out long storage periods exceed the limits given for them in this 

 publication. In addition, there is always the possibility that fluctu- 

 ations in temperature will cause condensation 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 

 " flywheel " 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 temperature changes occur more 

 slowly. For this reason small storage rooms generally will require 

 closer attention than large ones. 



HUMIDITY OF STOEAGE ROOMS 



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

 tion to the keeping quality of the products held in them. If it is too 

 low, wilting is likely to occur in most fruits, vegetables, cut flowers, 



