Is there any way to slow the ripening of bananas?
Most people store bananas on the countertop, and we wondered if chilling the fruit could slow ripening. To find out, we left 12 pounds of bananas at room temperature for three days until they were perfectly ripe (signified by a firm but yielding texture). We then moved half of the bananas into the refrigerator, leaving the remainder at room temperature.
For the next few days, the bananas were nearly indistinguishable. After four days, however, the room-temperature fruit became markedly soft and mushy, while the refrigerated fruit remained firm, despite blackened skins. We continued to taste the refrigerated bananas after the room-temperature samples had been discarded and were delighted to discover that they lasted an additional five days (so, almost two weeks after purchase) before the flesh became overripe.
The explanation is simple: As a banana ripens, it emits a gas called ethylene and develops acids that aid in ripening. Cool temperatures slow down the production of ethylene and acids, thereby decelerating ripening. However, refrigeration also causes the cell walls of the peel to break down, releasing enzymes that cause the formation of black-brown pigments.
Source: Cook's Illustrated