Why Do Mushrooms Turn Brown and Slimy So Quickly in the Fridge?

Mushrooms turn brown quickly in the fridge because an enzyme called polyphenol oxidase stays active even after harvest and darkens any surface exposed to air. This is a relative of the same family of enzymes that makes a cut apple turn brown. What speeds up the sliminess?Mushrooms have no protective skin and are mostly made of water, which makes them far more vulnerable than other vegetables to both losing moisture and absorbing too much of it. Mushrooms kept in a sealed plastic bag trap their own moisture inside; that trapped moisture both speeds up browning and creates a slimy environment on the surface that is well suited to bacterial growth. What is the right way to store them?Storing mushrooms in a paper bag, or wrapped in newspaper, gives far better results than a plastic bag; paper absorbs excess moisture and leaves a breathable environment around the mushrooms. Keeping mushrooms unwashed until needed also extends their life; washing adds extra water to their surface, which can create the same problem as moisture trapped in a plastic bag. That is why mushrooms are usually wiped with a damp cloth right before use instead. Storing them in a relatively less humid part of the fridge, such as the crisper drawer, also helps mushrooms stay fresh longer; an overly humid drawer can overwhelm the paper bag's absorbing capacity and recreate the same problem. Sliced mushrooms spoil far faster than whole ones; the larger the cut surface, the more area is exposed to the enzyme reacting with air, which is why slicing is usually left until right before use. A little surface browning alone does not mean the mushrooms need to be thrown out; a mild color change on the surface is usually still fine to eat, but a clearly slimy texture or a bad smell means the mushrooms should be discarded. Some mushroom types are more resilient than others; commonly eaten types like button mushrooms can stay fresh for a few days, while more delicate types like beech mushrooms can spoil much faster. Wild or organically grown mushrooms generally have a slightly lower moisture content than mushrooms grown commercially in intensely humid conditions, which can help them stay fresh a little longer than button mushrooms. Cooking mushrooms that have browned slightly is generally safe; heat already darkens mushrooms during cooking anyway, so a lightly browned mushroom becomes almost impossible to notice visually once cooked. The original supermarket packaging with an absorbent pad sometimes works better than a plastic bag for the first few days, since the pad soaks up excess moisture; but over the longer term it still does not replace transferring the mushrooms to a paper bag. Keeping mushrooms away from other strongly scented foods also helps preserve freshness; mushrooms readily absorb odors and may lose their own flavor if stored near pungent foods such as onions. Store mushrooms in a separate, closed section of the refrigerator to preserve both freshness and flavor.