Why do mushrooms turn dark when cooked?
Show answer & explanation
Answer: Polyphenols oxidize when heated
Releasing stored melanin — Wrong. Mushrooms do contain melanin-like compounds, but darkening is primarily from polyphenol oxidase enzyme acting on phenolic compounds.
Absorbing oil and seasonings — Wrong. Color change happens even without oil. Darkening is from enzymatic browning—polyphenols oxidizing when exposed to heat and oxygen.
Polyphenols oxidize when heated ✓ — Correct! Mushrooms contain polyphenol oxidase enzyme and phenolic compounds. Cutting and heating breaks cells, mixing these together. The enzyme oxidizes phenolics, creating brown melanin-like pigments (similar to apple browning). It's enzymatic browning, not caramelization. Lemon juice slows it by denaturing the enzyme!