If you want to prevent the bananas from becoming overripe before you are ready to eat them, don't keep them attached to one another. 'To keep bananas from browning quickly, break up the bunch and separate,' advises StopFoodWaste (opens in new tab). Keep bananas away from other fruit for maximum life, too.
Dividing your bananas and wrapping them individually is the best way to prevent the ethylene from traveling down the fruit. Plus, when you're ready to eat your bananas, there's no need to unwrap the stems.
Separate 'em!!! You see, as most fruits, bananas especially, ripen, they give off Ethylene gas and this Ethylene gas causes any nearby fruit to begin the ripening process. This is why a bunch of bananas all ripen at the same time, so here's the way to slow that process down and control it.
According to the US Department of Agriculture, the desired storage temperature for bananas is 56 to 58 degrees Fahrenheit. That means that bananas are best stored at room temperature—so your countertop really is the right place for them.
The theory behind this myth is that bananas begin producing ethylene as they ripen and by disconnecting them at the stem, their individual exposure to the ethylene production is reduced. The ethylene production is also said to be higher as a bunch.
Keep them cool and protected from the light: Bananas should be stored at around 12°C, as they will ripen quicker if they are too warm. A darker room without direct sunlight is ideal.
Supermarkets store most fruits in large refrigerated coolers in the back room. The fruit is pulled from the sales floor each night, and placed in the cooler to extend shelf life. Then it's restocked, & rotated the next morning. Some fruits & vegetables do not require refrigeration and are left on display overnight.
Ditch the Plastic Bag
Bananas that are stored in plastic bags will ripen faster. Instead, keep your bananas at room temperature in a cool, dark place to be sure they receive fresh, well-ventilated air. Bananas sitting in direct sunlight or near the stove will shrivel up and turn brown at a faster rate.
However, if you sprinkle them with a little lemon juice, it lowers the pH levels and will keep browning at bay. Following the lemon trick, put them in the fridge, either wrapped in plastic wrap or in an airtight food storage container or bag. Stored this way, sliced bananas can stay fresh for three to four days.
Bananas, like many fruits, release ethylene gas naturally, which controls enzymatic browning and ripening of not just itself, but other fruits nearby. Much of that offgassing takes place at the stem—or the crown—of the banana. By wrapping the crown of a bunch, you slow down the ripening process a bit.
Bananas grow in hot climates, so they are unused to the cold. If they're kept at a cold temperature, the enzymes that enable them to ripen are inhibited. And as those enzymes become inactive, other enzymes operate more efficiently. Some cause cell damage, while others (browning enzymes) cause the skin to blacken.
On the flip side, if you're hoping to serve dinner guests guacamole a few days from now and you've found yourself with an avocado that's almost too soft, there's a super simple way to slow the ripening down. Simply place your ripe fruit in the fridge. The cooler temperature will slow the effects of ethylene gas.
“They can be picked a little too early, in a state that does not allow them to ripen up.” In the store, a very green color could signify that, he said, so “look for organic bananas that are yellowing, meaning they were at the right stage when they were picked.”
Try speed-ripening bananas in the oven. Preheat the oven to 300 degrees F (150 degrees C) and line a baking sheet with silicone or parchment. (The bananas may leak a little during baking.) Place unpeeled bananas on the baking sheet leaving some space between them, and bake for about half an hour.
Don't leave ripened fruit or vegetables—like bananas, onions, tomatoes, or potatoes—exposed; keep them in the refrigerator until the problem is resolved. Fruit flies also tend to like alcohol and other sugary drinks, so be wary of keeping things like an open bottle of wine and juice products out on the counter.
Bananas are tropical fruits, and, in general, tropical fruits don't handle cold storage well. That's why the best way to store bananas is at room temperature, not in the fridge, especially when they're green and not yet ripened.
Wrap Banana Stems:
Bananas release ethylene gas through their stems. The more gas that is released, the riper the fruit. So by wrapping the ends of the stems in plastic wrap, you prevent or slow down this gas from escaping.
High amounts of ethylene cause the yellow pigments in bananas to decay into those characteristic brown spots in a process called enzymatic browning. This natural browning process is also observed when fruits become bruised.
Just toss your banana slices in some lemon juice to inhibit enzymatic browning. Full coverage, particularly on the cut sides, will help prevent the slices from turning brown. In addition to lemon juice, vinegar will also work.
Ultimately, as long as your banana is not moldy, and is not slimy or overly soft and squishy when you remove the peel, it is safe to eat brown bananas.