How Can You Tell Dried Mushrooms Have Gone Bad?

Dried mushrooms most often spoil by absorbing moisture and going soft, or by developing mold spots; properly dried, well-stored mushrooms stay firm, crisp and lightly aromatic, and losing any of those qualities is a warning sign.

What do moisture and mold look like?

Dried mushrooms left in a humid cupboard without a fully sealed bag absorb ambient moisture; the pieces turn flexible and no longer crackle when crushed by hand. At this stage there may not be mold yet, but the mushrooms have become highly prone to it and should be used soon or discarded.

If you see white, greenish or blackish fuzzy patches on the surface, the mushrooms have molded; in dried mushrooms these spots can be confused with powdery mushroom crumbs, so look closely and check whether the texture actually feels fuzzy to the touch.

What does a change in smell tell you?

Fresh dried mushrooms smell faintly earthy and nutty; if that scent is gone and replaced by a moldy or stale smell, the mushroom has lost its aroma even if it still looks intact, and it's often already starting to spoil. If soaking produces a slimy, mushy texture instead of the expected softening, the mushrooms shouldn't be used.

Dried mushrooms should also be checked for pests; thread-like webbing or tiny holes inside the package usually point to pantry pests, and the whole batch should be thrown out.

Storing dried mushrooms in an airtight jar, in a cool, dark cupboard, keeps them good for months, even close to a year; but since air gets in every time the package is opened, moisture needs to be checked regularly.

What do the soaking water and mushroom type change?

Don't pour out the water used to soak dried mushrooms before using them; it carries the mushroom's aroma and can be used in soups and sauces. But if that water is foamy or cloudy, the mushrooms had likely already spoiled before soaking, and both the mushrooms and the water should be discarded.

Different mushroom varieties (oyster mushrooms, morels, porcini) dry to different densities and so resist spoilage differently; thinly sliced, delicate mushrooms absorb moisture faster and spoil more easily, while thicker, meatier varieties hold up a little longer.

When buying dried mushrooms, it helps to check their color through the package's clear window; pale, dusty-looking pieces or ones clumped together can mean moisture already got in before packaging. Vacuum-sealed dried mushrooms stay fresh longer than ones sold in open containers, since sealing minimizes contact with air.

Home-dried mushrooms (oven-dried or sun-dried) tend to have a more variable moisture content than commercially produced ones; an insufficiently dried home batch can mold within a short time of being packaged, so home-dried mushrooms are worth checking more often during the first few weeks.