Maturity at harvest is the most important factor that determines storage-life and final fruit quality. Immature fruits are more subject to shrivelling and mechanical damage, and are of inferior flavour quality when ripe. Overripe fruits are likely to become soft and mealy with insipid flavour soon after harvest. Fruits picked either too early or too late in their season are more susceptible to postharvest physiological disorders than fruits picked at the proper maturity. All fruits, with a 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. 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) fruits that are not capable of continuing their ripening process once removed from the plant, and 2) fruits that can be harvested mature and ripened off the plant. Group 1 includes berries, cherry, citrus fruits, grape, lychee, pineapple, pomegranate, and tamarillo. Group 2 includes apple, apricot, avocado, banana, cherimoya, guava, kiwifruit, mango, nectarine, papaya, passion fruit, pear, peach, persimmon, plum, quince, sapodilla, sapote. Group 1 fruits produce very small quantities of ethylene and do not respond to ethylene treatment except in terms of degreening (removal of chlorophyll); these should be picked when fully-ripe to ensure good flavour quality. Fruits in Group 2 produce much larger quantities of ethylene in association with their ripening, and exposure to ethylene will result in faster and more uniform ripening.
