ISHS Acta Horticulturae 175: Symposium on Physiology of Productivity of Subtropical and Tropical Tree Fruits
TEMPERATURE MANAGEMENT AND CHILLING INJURY OF TROPICAL AND SUBTROPICAL FRUIT |
| Author: | B.I. Brown |
| Abstract:
Refrigeration is an important means of maintaining fresh quality while extending the postharvest life of highly perishable tropical and subtropical fruits. Rapid postharvest cooling and cool storage treatments are outlined. However the application of refrigeration to fruits of tropical and subtropical origin is limited by their sensitivity to cold stress (termed chilling injury) at temperatures below about 13°C. The mechanism of chilling injury is discussed briefly as well as areas of research being studied to elucidate the physiological and biochemical processes involved. Methods used for the alleviation of chilling injury are given. The effects of preharvest and postharvest chilling temperatures are discussed in relation to various fruits such as tomato, pineapple, atemoya, avocado, banana, mango, papaya and guava. The quality of fresh fruit and vegetables at harvest is determined by factors such as climatic environment, crop cultural practices, variety, maturity, pests and diseases. Postharvest quality maintenance is also influenced by factors which may be physiological, pathological, physical or combinations of these three (1). In postharvest storage, the factors which define the storage environment are temperature, relative humidity and atmospheric composition. Of these, temperature management is the most important factor in the maintenance of fresh quality by reduction in the rate of respiration, transpiration, enzymic activity, and growth and spread of micro-organisms (2). The overall benefits of cooling of fresh produce are increased profits and greater market flexibility (3). Rapid cooling of fresh produce involves the removal of field heat by the use of refrigeration. The initial cooling, termed precooling, also requires energy for removal of heat of respiration, heat transmission through cool rooms and heat leakage from outside air. Methods for cooling fresh produce are room cooling, forced air cooling, hydrocooling, vacuum cooling and ice packing after precooling. Of these, forced air cooling has proved to be the most effective method of fast cooling. Whilst the postharvest storage of produce at low temperature is beneficial, all aspects of metabolism of the produce are not suppressed to the same extent. Continued activity of some metabolic systems at low temperature can lead to cellular dysfunction and collapse. Metabolic disturbances occurring at reduced temperature are usually categorised as chilling injury (which affect tropical and subtropical fruits in particular) and physiological disorders (which affect mainly deciduous tree fruits such as apple, pear, stonefruits and citrus) (4). | |
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