|MadSci Network: General Biology|
Chilling injury occurs below 15 degrees C but above freezing with the chilling temperature varying depending on the particular species. Banana is one of the most sensitive fruits because it develops injury below about 12 degrees C. There are two main ideas of what causes the chilling injury to tropical and sub- tropical fruits and vegetables. One is that below a certain temperature the physical state of cell membranes changes allowing leakage of toxic substances from cells and cell collapse. The enzyme polyphenol oxidase is thought to cause the discoloration because it can oxidize phenolic compounds that leak from vacuoles and produce the dark color. The second idea is that the low temperature causes dissociation of enzymes and proteins into subunits which affects enzyme activity and cell structural proteins such as tubulin. Fruits and vegetables subject to chilling injury includes banana, lemon, lime, eggplant, tomato, avocado, cucumber, pineapple and papaya. Cold hardy fruits, such as apple and pear, are not affected as readily although prolonged storage at cold, but nonfreezing, temperatures may cause injury to apples as well. Apparently, cold hardy fruits evolved tolerance to chilling temperatures that tropical and sub-tropical fruits never did because they did not naturally encounter such temperatures. References Willis, R.B.H. et al. 1989. Postharvest: An Introduction to the Physiology and Handling of Fruits and Vegetables. London: BSP Professional Books. Fruits and Vegetables Subject to Chilling Injury Chilling Injury of Horticultural Crops
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