INFLUENCE OF FIELD CONDITIONS AND HANDLING OPERATIONS ON FRUIT QUALITY

摘要

Maturity at harvest is one of the most important factors that determines storage life and final fruit quality. Immature fruits are more prone to shriveling and mechanical damage, and have inferior flavor quality when ripe. Overripe fruits are likely to become soft and mealy with insipid flavor soon after harvest. Fruits picked either too early or too late in the season are more susceptible to postharvest physiological disorders than fruits picked at the proper maturity. All fruits, with few exceptions such as pears, avocados, and bananas, reach their best eating quality when allowed to ripen on the plant. However, some fruits are usually picked mature but unripe so that they can withstand the postharvest handling system when shipped long-distance (Dris et al., 1998; 1999). Most currently used maturity indices are based on a compromise between those indices that would ensure the best eating quality to the consumer and those that provide the needed flexibility in marketing. Fruits can be divided into two groups: 1) those not capable of continuing their ripening process once removed from the plant; and 2) those that can be harvested mature and ripened off the plant. Group 1 includes berries, cherry, citrus fruits, grape, pineapple, pomegranate, and tamarillo. In group 2 fruits such as apples, apricot, avocado, banana, kiwifruit, mango, passionfruit, pear, peach, and plum are included. Group 1 fruits produce very small quantities of ethylene and do not respond to ethylene treatment except in terms of degreening and removal of chlorophyll. These fruits should be picked when fully ripe to ensure good flavor quality. Fruits in group 2 produce much larger quantities of ethylene during ripening and exposure to ethylene results in their faster and more uniform ripening. Fresh fruits are highly perishable. Quality declines rapidly after harvest, especially if proper postharvest handling procedures are not followed. Change in color, texture, nutrition, and flavor all affect their market quality. Fruit tissues are composed of living cells and continue to respire, metabolize and lose moisture after harvest. Other factors which increase deterioration include bruising, mechanical injury, physiological, and pathological disorders. Quality can be maintained by harvesting fruits at optimal maturity and storing them at proper temperature, humidity and atmosphere. Good sanitation reduces losses caused by postharvest diseases. In order to maintain product quality, the food processing industry relies on sensory evaluation by panels of expert human noses, and of all the human senses, smell has been the most difficult to define objectively. Recent advances in the use of a combination of nonselective gas sensors and pattern recognition techniques based on the human olfactory system have allowed complex aromas to be measured and characterized. However, these systems are complex, and development of robust field devices capable of evaluating complex aromas of fresh produce, as well as at different stages in the food manufacturing process would offer producers a means of systematically improving quality and hence value (Dris, 1998; Dris and Niskanen, 1997, 1999).