Why bananas should not be kept in Refrigerator?

Banana peels can turn brown or black when refrigerated. The cells on the peels of tropical fruits like banana get damaged when stored under cold conditions (Chilling Injury). This releases some phenolic compounds that get oxidized by enzymes like polyphenoloxidase leading to the darkening of the peel. Chilling injury can result in great losses in the quality and shelf life of the fruit. Fruits and vegetables subject to chilling injury includes banana, lemon, lime, eggplant, tomato, avocado, cucumber, pineapple, jackfruit and papaya. Banana is one of the most sensitive fruits because it develops injury below about 12 degrees C. Apparently, cold hardy fruits, such as apple and pear, are not affected as they evolved tolerance to chilling temperatures. The blackening of the banana skin is caused by the release of enzyme, polyphenoloxidase (PPO). This is an oxygen-dependent enzyme, which polymerises naturally occurring phenols in the banana skin into polyphenols similar in structure to melanin formed in suntanned human skin.