The internet has been going bananas recently over a video circulating via Hellou.com, claiming to “unripen” a rotten old piece of fruit, using rice and heat.
So after spending 2 minutes of my life watching a guy blow-dry a banana, we decided to investigate (because science).
Take a look at the video here if you feel so inclined.
How is this possible? Is it even possible? The idea of reviving a battered piece of fruit seems thrifty at best, but let’s take a look at the science behind it anyway.
Bananas are classed as a climacteric fruit, which means that they continue to ripen after picking. Ripening of fruit is associated with composition change, ie, starch converting into sugar. Ethylene gas, a ripening hormone produced by the plant, plays a major physiological role in the process. While the fruit is still attached to the plant, special receptors in plant cells bind to the ethylene, keeping the fruit ripening genes from activating. Once a fruit is picked, plant genes ETR1 and CTR1 turn off, which causes a domino effect that ultimately results in the release of ethylene and turns on other genes that make various enzymes. These include: pectinases, which break down cell walls and soften the fruit; amylases, which convert starch to simple sugars; and hydrolases, which degrade the chlorophyll in the fruit, resulting in the color change – in this case from green to yellow. This is believed to invite animals to eat the fruit and disperse seeds via defecation.
As these processes continue and the cells within a banana denature, it eventually becomes rotten and pretty unappealing to eat.
Considering all of these chemical changes in composition within the fruit as it ripens and rots, is it possible to revive a gross old banana using rice and heat?
Debate has previously raged on how to store and best extend the life of bananas – should they be left at room temperature or stored in the fridge? Storing bananas in a cold environment drastically slows the conversion of starch to sugars, which means that the flesh stays good for longer. However, when they are placed in the fridge, an enzyme (polyphenyl oxidase) combines with phenols in the peel to create polyphenols, which causes the outer skin to turn brown. So although the fruit inside is still tasty and ripe, the skin looks rotten.
What conclusions did we draw from our investigation? We actually did try this ourselves in the office, and were left with nothing but a still-rotten banana. Perhaps unsurprisingly, we simply have another case of the internet leading us up the garden path for reasons that only the individuals coming up with this rubbish will know.
You can't revive a rotten banana. This leaves us with two hypotheses – by placing the banana in the fridge, the banana flesh is preserved but the skin goes brown (which is what we're seeing in this video). Placing the banana in the rice removes moisture from the skin, and gently heating the banana back to a normal temperature may reverse the effects of cooling on the skin, restoring the color.
...That, or it's simply lighting or computer trickery.
IFLScience: answering the tough questions.