[英语课]

Great question, isn't it! The reason banana peels turn black quickly after peeling, but stay yellow for longer when unpeeled, comes down to exposure to air and enzymes. Here's a simple explanation:


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🍌 Why peeled bananas turn black quickly:

1. Exposure to Oxygen (Air):

When you peel a banana, the inner surface of the peel and the fruit are exposed to air.

This starts a process called oxidation.



2. Enzymes in the Peel:

The banana peel contains enzymes like polyphenol oxidase (PPO).

When the peel is damaged (by peeling), these enzymes react with oxygen and natural compounds in the banana.

This creates brown and black pigments (melanin-like compounds).



3. No Skin Protection:

The inner peel has no protection anymore, so it degrades faster—turning black or brown quickly.





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🍌 Why unpeeled bananas stay yellow longer:

1. Natural Skin Barrier:

The banana skin protects the inside from oxygen and moisture loss, slowing down the oxidation process.



2. Lower Enzyme Activity (Initially):

While enzymes are still present in the peel, they stay mostly inactive until the banana gets bruised or starts to ripen too much.



3. Controlled Ripening:

The yellow color is due to the breakdown of green chlorophyll during ripening.

This process is gradual when unpeeled, especially in cool or dark places.





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Summary:

Peeled banana = exposed to air → enzymes + oxygen = quick browning

Unpeeled banana = protected by skin → slower enzyme reaction = stays yellow longer


Let me know if you'd like tips to slow the browning of peeled bananas!