How to ripen bananas quickly: in the oven, in the microwave, or with egg

The common perception is that banana bread is simply a way to use up overripe bananas. But when you want to make it purely for pleasure, and the only bunch available is bright green and rock hard, you need to know how to ripen them quickly, or at least soften them. Several methods have been tried, depending on how quickly you need to start baking.

Chlorophyll gives the peel of a green banana its characteristic color. The fruit ripens by releasing ethylene, a plant hormone that breaks down this pigment, and carotenoids replace it until the peel turns yellow and eventually brown, similar to how green leaves turn orange-yellow in autumn. A green banana is composed mostly of resistant starches, which slowly convert into sugars: the pulp softens, sweetens, and acquires the texture needed for desserts and baking.

For breads and cakes where banana is part of the dough, it's best to look for brown or even black bananas, according to Jesse Szewczyk, senior editor of Test Kitchen. For a pudding or dessert with soft but visible chunks, however, "you should look for bananas that are perfectly ripe": yellow, but with spots. If you're in a real hurry, for example, because you have a loaf of chocolate chip banana bread for a dinner party in a couple of hours, you could consider ripening a green banana in the oven or microwave.

On the BA Bake Club podcast, senior test kitchen editor Shilpa Uskokovic suggested: “You can roast them [on a parchment-lined baking sheet] in a low oven (160°C) for 20 to 25 minutes until they’re soft inside, or you can microwave them in their skins [in 30-second intervals on a microwave-safe plate] to achieve the same effect.” These methods cook the banana rather than ripen it, and don’t transform the starches in the same way as natural ripening, though they do soften the flesh and make it slightly sweeter. Verdict: For soft-fleshed bananas, the microwave and oven are unbeatable for speed, but the flavor can be subpar.

Another option is to mash the green bananas with the eggs in the recipe. This method, suggested by Stella Parks of Serious Eats, takes advantage of the amylase present in the yolks, an enzyme that breaks down starch and plays a crucial role in banana ripening. By mixing the green pulp directly with the egg, the reaction quickly breaks down the starches, and after 30 minutes you have a purée ready for any banana baking recipe. Verdict: If speed and sweetness are what you're after, this is the best option, although the flavor won't be as complex as that of naturally ripened bananas.

Storing an unpeeled banana in a brown paper bag seems logical, as it traps its natural ethylene and accelerates ripening. However, in a room-temperature test, after three days, bananas stored in paper bags showed the same level of discoloration as those left on the countertop, and a plastic bag yielded identical results. Verdict: Wrapping a green banana in a paper bag won't hurt it, but it probably won't help it either.

Many people recommend placing apples in a high spot, like on top of the refrigerator, to ripen them faster, but in the test kitchen, the refrigerator had cabinets above it, so the method couldn't be tested. In a previous test, a creative grower found that bananas placed in that spot ripened the fastest: "They were the first to show brown spots," and it took about four days for them to show this unmistakable sign of ripeness. "And they continued to ripen faster than all the other fruits tested." Verdict: For fast, natural ripening, it's best to find the warmest spot in the kitchen, probably on top of an appliance like the refrigerator. It takes a few days, but the flavor is worth it.