Science may have the solution: a chemical "hydrogel" coating made from chitosan, derived from the shells of crabs and shrimp. Chitosan is already sprayed on lots of other fruits and vegetables to kill bacteria and keep produce fresh. And on Wednesday, Xihong Li of Tianjin University presented data at a meeting of the American Chemical Society showing that it can work to delay banana ripening -- bad news for fruit flies, good news for you.
"We found that by spraying green bananas with a chitosan aerogel, we can keep bananas fresh for up to 12 days," Li said in a statement Wednesday. "Such a coating could be used at home by consumers, in supermarkets or during shipment of bananas."
Like other fruits, bananas don't die when they're picked. They respire through their skin, taking in oxygen and expelling carbon dioxide. Increased respiration means quicker ripening. The chitosan coating used by Li and his colleagues slowed down respiration enough to keep the fruit fresh.
Bananas also release a compound called ethylene, which encourages ripening. So leaving a bunch of bananas in a bag will trap a lot of ethylene gas in there, which makes them ripen faster. Other fruits and vegetables produce ethylene too, so keeping your banana in the same bowl as a bunch of apples will hasten its progress toward gooey oblivion.
Chitosan, with its seafood origin, could possibly pose problems for strict vegetarians and vegans, but it wouldn't be the first food additive that flew under the radar. Shellac, which you might primarily think of as something to polish furniture, is also applied to apples to replace natural waxes lost during the cleaning process. It's also made from a resin secreted by the female lac bug. Starbucks caught flak from its crunchier customers after it was revealed that the coffee giant was using crushed beetle shells to color its strawberry frappuccinos.
Still, if you're not squeamish about animal products, chitosan could be a good way to keep good bananas from going bad.