Shoppers should purchase the freshest mushrooms at the grocery store or farmers' market. Mushrooms should be dry, solid, and smooth.
Dirt on mushrooms is okay. Wipe any filth off before storage. If the mushrooms seem dirty, don't rinse them until you use them.
If your mushrooms go from firm and plump to slimy, they're rotten. If they're dry or shriveled, toss them.
If your mushrooms have changed color or developed black patches or fuzzy mold, toss them. Most mushrooms aren't fragrant, thus an unpleasant stench might indicate spoiled mushrooms.
"Enoki mushrooms, which are among the most delicate types, might go bad more rapidly. If you buy mushrooms, you should have a meal in mind for them."
Because there are so many various kinds of mushrooms, each with its own distinct taste and texture, some may spoil sooner than others.