How to Ripen Bananas
The very best technique according to a plant scientist who studies fruit ripening.
By Lesley Porcelli for Food Network Kitchen
Lesley Porcelli is an editor and recipe developer based in Syracuse, New York.
Oh, the angst of having a bunch of green, rock-hard bananas on hand when all you crave is a single ripe one. Don’t be tempted to eat one too early. Biting into a banana before it’s reached its prime is about as unappealing - pun intended - as chewing on cotton balls.
What’s the difference between ripe and unripe bananas?
To get to the bottom of this question, we chatted with James Giovannoni, a USDA scientist with the Boyce Thompson Institute who specializes in fruit ripening. He explains why bananas you pick up from the supermarket might be slightly green and unripe. “Unless you live in Southern Florida or have been south of the border, you haven’t tasted a banana that’s ripened naturally,” says Giovannoni. Bananas sold in the States for the most part come from Central and South America, where they are harvested prematurely and then kept in a low-oxygen, high carbon-dioxide environment to naturally slow down the ripening, so that they will keep through days of transportation and storage. “The warehouses treat the bananas with ethylene” - the hormone that is both responsible for and a product of ripening - before putting them on supermarket shelves, says Giovannoni. This has the effect of “waking” the bananas from their state of suspended animation and starting them on their path to ripening.
During ripening, the banana converts its starches to sugars, sweetening and softening the flesh within. Its acid levels also recede, increasing the sensation of sweetness, and the fruit develops those banana-y aromas that complete its signature flavor profile.
How can I ripen bananas quickly?
While there’s no tactic that will magically transform the greenies into fruit that’s instantly ready to be eaten out-of-hand, you can speed up the process by harnessing the ethylene that the plant naturally gives off, says Giovannoni.
“The quickest method is to close the bananas in a paper bag with another fruit that’s already ripe, like an avocado or more mature banana,” says Giovannoni. The ripe fruit will give off quite a lot of ethylene, and trapping the fruits together in the bag will jump-start the process on the green bananas.
Why the paper bag? “A paper bag is porous, so you’ll increase the concentration of ethylene, but it won’t create a sealed environment [like plastic would], where the fruit would consume all the oxygen and then go anaerobic,” he says. “That’s when yucky things happen, like the growth of anaerobic microbes that contribute to food spoilage.” Even placing the green bunch in a paper bag by itself will speed up the maturation process, capturing its own ethylene that would otherwise disperse in the air, although it will happen more slowly if not in the presence of a riper piece of fruit.
Surprisingly, stress and injury also cause fruit to ripen quickly because Ethylene is used as a signal in stress response. “You could drop your fruit on the counter a couple of times,” Giovannoni says with a chuckle, “but I don’t know that I would recommend it.”
A Step-By-Step Guide to Ripening Bananas
What You’ll Need
- One paper bag (a repurposed shopping bag is fantastic)
- One piece of fruit that’s already ripe, such as another ripe banana or an avocado
What to Do
- Place the unripe bananas in the paper bag with the ripe fruit.
- Roll up the end of the paper bag in order to trap the ethylene that’s released around the unripe bananas.
- Wait a day or so. The bananas might be ripe by the end of day one, but they’ll certainly be ripe by the end of day two.
What should I do if my bananas ripened too fast?
Took them too far? Pop the bananas into the fridge to arrest the ripening. Yes, the skin will blacken, but the flesh inside will stay just-right for a few days longer. Or go the time-tested route of bakers everywhere: Peel them, then freeze them in a plastic bag so that you always have a stash of bananas that are ready to be turned into something yummy (like Food Network Kitchen’s The Best Banana Bread).