Document LKJKkm7xVd1qJBxG8X6Ez0Bv5

494 CVrHt IATUPTIELfRX 4<t6U H, W. VonLoesecke: Banana* (Interscienee Publishers, lot.. New York, 1949). C. W. Wanilaw: Tropical Fruits and Vegetable*--An Account of Their Storage and Transport (Low Temperature Research Sta tion, Memoir No. 7. Trinidad). B. K. Watt ana A. L. Merrill: Composition of Food*--Raw, Processed, Prepared (USDA Handbook No. 7, 1950). A. W. WeQa and H. R, Barber: Extending (he Market Life of Packaged Studied Not* (Marketing Research Report 329, USDA, 1959). T. M. Whiteman: Freezing Points of Font*. Vegetable* and Florist Stocks (Marketing Research Report 196, USDiC 1957). W. R. Woolnch, A. H. Cooper, P. W. Scates, A. L. fimith( and T962 Guide And Data BooV M. Tucker: The Latent Beat of Foodstuff* ^Tennessee Aan+it.~.. . Experiment Station Bulletin 11, 1933). *~**vnu S. T. Worthington and D. H. Scott: Strawberry pbvnt staran umn;r polyethylene linen (American Nurserymen, VoL 105 k? 9, May 1957, p. 13). ' ' R_ C. Wright: Irwestigatums on the Storage of Nuts (Tecfutieiri Bulletin 770, USDA, 1941). ^ R C. Wright, D. BL Rose, and T. M. Whiteman: The Commer cial Storage of Fruits, Vegetables, Florist and Nursery (USDA Handbook No. 66,1954). P. T. Ziegler: The Meat W* Eat (Interstate Printers and Pubs fishers, Danville, Illinois, 1958). CHAPTER 47 STORAGE OF APPLES, PEARS, GRAPES, AND BANANAS ^ijVrT- Storage Temperature, Air Purification, Controlled Atmosphere, Storage Disorders; Pears: Confro/Jed Atmosphere, 5/ora9e Disorders; Grapes: Storage Environment, Fumigation; Design and Operation of Fruit Storage Houses; Bananas: Harvesting and Transportation, Ripening, Effect of Temperature, Ripening Rooms, Refrigerating, Heating, and Humidity Systems, Controls, Packing and Shipping A LL fresh fruits are alive and remain so during storage and /^marketing and even for some time after they are no longer ia marketable condition. Being alive, they respire using stored constituents, primarily sugars, and oxygen from the air to produce carbon dioxide and energy (heat). The reactions ue extremely complex. The environment in which a harvested fruit is placed may greatly influence not only its rate of respira tion but also other products formed in related chemical reac tions within the fruit. All of these influence storage and market fife. In addition to. deterioration after harvest by chemical changes within the fruit, two other forms of deterioration are important during storage and marketing; namely, dessication and diseases caused by microorganisms. Regardless of the kind of deterioration, its rate is greatly influenced by temperature. Deterioration of fruits by their own life processes or by micro organisms is reduced as temperature is lowered, so that the marketable life span may be perceptibly extended. The specific relationships between temperature and rate of deterioration vary considerably between commodities and diseases. However, a reasonably accurate generalization assum ing a deterioration rate of 1 for a fruit at 30 F would be as shown in Table 1. From these figures, it is obvious that the best temperature to slow down deterioration resulting from a bruit's own living processes or from pathogens is the lowest tempera ture'that can safely be maintained without freezing the com modify. This would be approximately 1 to 12 F deg above the freezing point of the fruit in the most modem plants with effi cient air distribution, and approximately 3 to 4 F deg above the freezing point in structures of older design. . Some fruits will not toleratelow storage temperatures. Severe physiological disorders that develop because of exposure to low temperatures are commonly classed as ckilling injury. The precise reasons for this behavior are not understood, but it is known that normal biochemical functions are upset. The banana is a classical example of a fruit displaying chilling injury symptoms, and storage temperatures must be elevated accord ingly. Certain apple varieties also exhibit this characteristic sod for prolonged storage must be held at a temperature well above that usually recommended. The degree of susceptibility of an apple variety to chilling may vary with climatic and cul tural factors. The third important factor of deterioration, namely, dessicataon or water loss, results in shrivelling of the fruit and is strictly a physical factor related to the evaporative potential of the air. It may he expressed directly as vapor pressure deficit (Fn), a term indicating the combined influence of temperature relative humidify (RH) on the evaporative potential of the air, normally expressed in millimeters (or inches) of mer cury as follows: 100 - (RH) Vo - p 100 (D pB = vapor pressure deficit, millimeters (or inches) of of mercury. p vapor pressure of water at a given temperature, milfimeten (or inches) of mercury. (RH) -- relative humidify, percent. For example,.comparing the evaporative potential of sir in storage rooms at 32 F and 50 F dry-bulb, with 90 percent rela tive humidity in each room, the vapor pressure deficit at 32 F is 0.46 mm Hg, while at 50 F, it is 0.92 mm Hg. Thus, if all other factors were equal, commodities would tend to lose water twice as fast at 50 F dry-bulb as at 32 Fat the same RH values. For equal water loss at the two temperatures, the RH would have to be maintained at 95 percent at 50 F in comparison to 90 per cent at 32 F. These comparisons are not precisely true because the water in fruits contains a sufficient quantity of dissolved sugars and other chemical materials to cause the water to be in equilibrium with water vapor in the air at 98 to 99 percent RH instead of 100 percent RH. Lowering the vapor pressure deficit by lowering the air temperature is as excellent rne*mn Qi reduc ing water loss during storage. Other important factors in fruit dessication include fruit size, the kind of protective surface on the fruit, and air move ment. Of these, the storage operator canoontrol only the last, and this control will be greatly influenced by the container, kind of pack and stacking arrangement or, in'other words, the ability of the air to move past individual fruits. As a rule, shrivelling does not become a serious market prob lem until fruits have lost about 5 percent of their weight, but any loss reduces the salable tonnage. It is not practicable to Table 1 ... - Approximate Relationship of Temperature and Deterioration Rote due to Physiological Processes and Microorganisms Temp, F ' 68 50 41 37 32 30 Deterioration Kate 8-10 4- 5 3 2 1.25 1 495