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josie's avatar

Why does a banana peel instantly begin to turn brown after it is removed?

Asked by josie (30934points) February 18th, 2011

I select a banana to snack on. It is, by my standard, perfect to eat. The peel is uniformly yellow, with a few scattered small brown freckles. The perfect texture and sweetness.

But, when I peel the banana, the peel almost instantly begins to turn dark, almost before my eyes.

What happens when I peel the banana, that causes the peel to change so much more quickly than if I left it on?

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8 Answers

marinelife's avatar

It doesn’t just happen when you eat one. That just speeds up the process.

“Bananas left outside will begin to turn brown within a few days. This occurs because bananas contain an enzyme called polyphenol oxidase that reacts with oxygen and coats the banana with a sort of rust that accounts for the dark brown color.”

Source

iamthemob's avatar

@marinelife beat me to the punch. Just remember that, even though we need it to live, oxygen is a corrosive gas.

Seelix's avatar

Yup. Same thing happens to sliced apples.

LuckyGuy's avatar

I too eat bananas. Let’s assume there are two equal bananas sitting on my kitchen counter with just the right number of freckles (432 ). If I peel one and eat it, the peel will be black in an hour or two while the one on the counter will have 435 freckles. In fact I put the peel in my burnable trash bag where it ends up heating my house for a short while. I don’t know why the peeled peel turns black faster unless it is oxygen getting at it from two sides instead of one. One thing I am sure about – the second banana will be gone in a coupe of hours.

thorninmud's avatar

There’s considerable evidence that the polyphenol oxidase reaction is a defense mechanism that boosts the plant’s resistance to insects and infection when some injury has occurred. The poor banana is, in effect, scrambling its defensive forces to protect itself in response to your heartless attack.

LuckyGuy's avatar

@thorninmud Putting it out of its misery is the least I can do.

thorninmud's avatar

@worriedguy Just make it quick

Dutchess_III's avatar

Bananas they grow in the tropical equator, so don’t put your bananas in the…refridg-er-ator!

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