Why do bananas turn black?
Show answer & explanation
Answer: Enzymes oxidize polyphenols
Enzymes oxidize polyphenols ✓ — Correct! As bananas ripen, cell walls break down releasing polyphenol oxidase enzyme. This enzyme reacts with phenolic compounds and oxygen, creating dark melanin pigments - the same process that browns apples! Ethylene gas produced by the banana accelerates ripening. Cold slows this enzyme activity, which is why refrigerated bananas stay yellow longer (though the skin still darkens).
Sugar caramelizes naturally — Wrong. Caramelization requires heat above 160°C to break down sugars. Bananas blacken at room temperature through enzymatic oxidation. Though bananas do convert starch to sugar as they ripen, this doesn't cause the dark color.
Skin cells die over time — Wrong. While cells do change during ripening, the blackening is specifically from enzymatic browning. It's polyphenol oxidase enzyme reacting with phenolic compounds in the presence of oxygen, creating melanin pigments, not just cell death.
More Food & Nutrition questions
- Parmigiano Reggiano is made with milk, salt, and rennet only, so why can older pieces taste more savory or spicy without extra seasoning?
- Why does a Parmigiano Reggiano wheel wait until at least 12 months for the official selection mark instead of being fully approved when it is molded?
- How can Parmigiano Reggiano keep developing flavor after its starter bacteria have done their early acid-making job?
- A young Parmigiano Reggiano can taste milky, while older wheels lean nutty, spicy, or broth-like; what pushes the flavor away from plain dairy?
- Why does aging Parmigiano Reggiano from 12 months to 36 months not matter much for removing lactose?
- Why can older Parmigiano Reggiano turn crumblier and grainier instead of simply becoming a harder block?