In international trade, bananas are the most commonly traded fruit after those of the citrus family. To ripen, temperature is elevated and fruit is exposed to ethylene gas. It is possible to harvest required fruit only, by cutting the most developed upper hands from the bunch and leaving the rest for another week. Once picked, bananas ripen at variable rates largely dependent on temperature. A hand enclosed in a plastic bag with an apple ripens faster.
Bananas are much better when harvested mature.
This is when the fruit have filled out and lost their angular appearance. If allowed to ripen on the plant, bananas will almost certainly be attacked by fruit bats. As bananas ripen, starch is converted to sugars, the fruit softens and the colour changes from yellow-green, to yellow, then gold, and eventually to almost brown, becoming mottled with dark spots. Under hot conditions, fruit ripens very quickly, but the skin colour turns a dirty green and the fruit becomes mushy. During summer months it is advisable to ripen bananas in the coolest room, near floor-level, or in an air conditioned area.