3254 



STORAGE 



STORAGE 



and when the air of the storage rooms becomes exces- 

 sively dry, the fruit may become seriously wilted by 

 excessive evaporation. The reduction of the tempera- 

 ture of the air reduces its water-holding capacity; con- 

 sequently, as the air temperature is reduced to the 

 freezing-point or below, all the excess moisture is 

 removed and the air becomes saturated with water 

 vapor for the temperature at which it is held. The 

 total volume of water vapor is thereby greatly reduced. 

 When the temperature of the air rises without the 

 addition of moisture, its capacity for absorbing mois- 

 ture from the fruit increases and, consequently, the 

 drying effects due to refrigeration may be seriously 

 overdone. The most satisfactory humidity condition 

 in the storage room has never been correctly deter- 

 mined. Experience shows that the humidity condition 

 should be as high as possible to prevent shrinkage from 

 evaporation, but without danger from excessive mois- 

 ture, which may induce the growth of mold. 



Excessive wilting of fruits in storage is not always 

 due to evaporation. Fruits which are picked in an 

 immature condition wilt and shrivel seriously under 

 the most satisfactory storage conditions. 



3704. Diagram showing ventilating air space and proper positions 

 of ventilators in a common fruit storage house. 



From what has been said, it will be seen that humid- 

 ity conditions in artificially refrigerated chambers 

 very largely take care of themselves, due to the ameli- 

 orating effects of the refrigeration of the air. The con- 

 trol of the conditions becomes more important at 

 high storage temperatures, -e. g., it is very important 

 in the storing of citrous fruits without artificial refrig- 

 eration. Under these conditions the humidity of the 

 storage rooms or cellars must be held relatively high, 

 because the higher temperature has a decided effect 

 upon the life activities of the fruits, and a corres- 

 pondingly high humidity is, therefore, essential. The 

 fruit must be very carefully watched; otherwise, mold 

 will occur when humidity conditions are too high. A 

 relative humidity of about 80 to 85 per cent at a tem- 

 perature of 50 F. has been found to be most satis- 

 factory under the conditions which exist in California 

 lemon-storage houses. It would not be safe to say that 

 this humidity percentage is exactly correct, because 

 the complexity of accurately measuring humidity 

 conditions under different temperature conditions 

 renders the problem very difficult. 



Common storage. 



The difference between common storage and cold 

 storage has been explained (page 3246). The principal 

 difference is that with cold storage, artificial refrigera- 



tion is used while in common storage there is no arti- 

 ficial refrigeration. Common storage is sometimes 

 referred to as "dry storage," inferring that cold stor- 

 age must necessarily be wet. This assumption is in- 

 correct; cold storage is not in any way connected with 

 moisture nor is it more likely to produce moisture in 

 storage rooms, provided they are carefully conducted, 

 than is common storage. Any excess of moisture in 

 the cold-storage room means some defect in the con- 

 struction of the plant or in its operation. It has been 

 said that cold-stored fruits are more moist when with- 

 drawn from storage than common-stored fruits. Here 

 again, the difference is due to the difference in the 

 temperature. The cold fruit from the artificially cooled 

 storage chamber, coming in contact with the warm 

 moist air, will condense moisture on its surface. Fruits 

 from the ordinary storage rooms may not be cold 

 enough to condense moisture; hence, the assumption 

 that the cold-stored fruit is more moist than that from 

 common storage. 



Common storage is not practicable for all fruits. 

 The very active or highly perishable fruits cannot be 

 held satisfactorily under common -storage conditions 

 because there are no ready means at hand to cool 

 them to the desired temperatures. Citrous fruits are 

 eminently adapted for common storage. The curing of 

 lemons is really a process of common storage. Winter 

 varieties of apples and pears are also suitable for com- 

 mon storage. This method of storage is used to a con- 

 siderable extent in New York and is coming into wide 

 use in the Pacific Northwest. In the operation of 

 common-storage rooms, dependence is placed on the 

 ventilation for the cooling. There is a vast difference 

 between ventilation due to the actual change of air 

 by the opening of windows or flues into the room and 

 the circulation of air. Ventilation means the admission 

 of outer air, and circulation may refer merely to the 

 movement of the air within the room or plant, the same 

 air being used over and over again. This distinction 

 is necessary because frequently the circulation of the 

 air within the room is designated as ventilation. 



In the operation of common-storage rooms, the rooms 

 are ventilated, or outside air is admitted, when its 

 temperature is low enough to cool the fruit. The ven- 

 tilators are closed during the day and during warm 

 periods, thus conserving to a certain extent the low 

 temperature obtained through the low -temperature 

 outside air. It is essential, therefore, that there be cold 

 nights or cold weather; otherwise, common - storage 

 plants become mere cool-storage chambers, and the 

 storage season is considerably shortened, due to the 

 fact that the relatively high temperatures result in a 

 high rate of life activities in the stored products. When 

 the temperature of the common-storage room can be 

 maintained somewhere near 32 early in the season 

 there is no apparent reason why the storage period 

 should not be extended to almost the same length of 

 time that can be obtained under cold-storage conditions. 



In the early part of the season, especially when 

 there are few cold nights, it is difficult to reduce the 

 temperature of the fruit to. the desired point. This is 

 the critical period, as the rapidity with which the 

 temperature of the fruit can be reduced determines the 

 length of time the fruit may be held in good condition. 

 It is easy to see, therefore, that under common-storage 

 conditions, usually the fruit must remain at a com- 

 paratively high temperature for a considerable length 

 of time. The ripening which occurs during this period 

 of high temperature cannot be offset by low tempera- 

 tures later on. The developments which take place in 

 this period of high temperature shorten the life span 

 under storage conditions, and when the temperature 

 is high and the fruit held warm for a considerable length 

 of time, the storage period may be very materially 

 shortened. There are frequent warm spells during 

 the fruit harvest, and the nights are not so cold. 



