Our Guide to Fresh Mushrooms

Neither plant nor animal, mushrooms are fungi that grow on the forest floor. There are around 1,000 edible varieties, but only about 20 are commercially cultivated. The mushrooms we buy in the supermarket are grown under highly controlled conditions on mushroom farms.

Mushrooms are noted for their characteristic flavor when cooked; they provide a savory, meaty umami taste to dishes. That’s because they are an excellent source of both glutamic acid and the nucleotides IMP and GMP, which combine to produce a strong umami taste. Since both glutamic acid and the nucleotides are nonvolatile and heat-stable, cooking does not destroy mushrooms’ ability to enhance the taste of food.

We recommend buying loose rather than packaged mushrooms so you can inspect their condition.
Pay attention to the following qualities:

Cap Size and Condition: Whole and intact with no discoloration or dry, shriveled patches. Pick mushrooms with large caps and minimal stems.

Moisture: Faintly damp but not moist or slimy.

Texture: Springy and light—never spongy.

Aroma: Intensely sweet and earthy. Avoid mushrooms that smell sour or fishy.

Maximizing the shelf life of mushrooms is all about balancing air circulation with moisture retention.

Loose Mushrooms: Store in a partially open zipper-lock bag, which maximizes air circulation without drying them out. Leaving the bag slightly open allows ethylene gas emitted from the mushrooms to be released, prolonging their shelf life.

Packaged Mushrooms: Store in their original containers, which are designed to “breathe,” maximizing the mushrooms’ shelf life by balancing the retention of moisture and the release of ethylene gas. If you open a sealed package of mushrooms but don’t use all the contents, rewrap the remaining contents in the box with plastic wrap and poke a few holes in the plastic wrap to allow moisture to escape.

DON’T wrap mushrooms in a paper bag or cover them with a damp paper towel, as many sources suggest. Both techniques speed up their deterioration.

Due to their high moisture content, fresh mushrooms are very perishable. But if properly stored, they can last at least a week.

How to Know When Mushrooms Go Bad
A slimy film on the cap and stem, mushy texture, and dark discoloration are the classic indicators of spoiled mushrooms.

That question has long been the subject of debate among cooks, since any water that mushrooms absorb during washing thwarts browning and prolongs their cooking time. So we tested how much water various types of mushrooms absorb by weighing them before and after washing.  

The upshot: Mushrooms with exposed gills (such as portobello and shiitake) absorbed lots of water, so it’s best to avoid washing these varieties. Instead, simply brush off any dirt with a pastry brush or paper towel. But varieties that don’t contain exposed gills didn’t soak up much water at all, so it’s fine to wash them as long as you do so before cutting them; their exposed flesh will absorb water like a sponge. (Note: Most cultivated mushrooms are very clean and don’t require washing in the first place.) 

Though it sounds counterintuitive, we found that simmering mushrooms in a small amount of liquid before sautéing them is the most efficient way to help them shed liquid so that they can then brown. Even better, this step allowed us to dramatically reduce the amount of oil necessary for sautéing. See how it works in our recipe for Sautéed Mushrooms with Red Wine and Rosemary.

Mushroom cell walls are made of a uniquely resilient, heat-stable polymer called chitin. This substance (which is also found in the exoskeletons of crustaceans such as shrimp and lobster) enables mushrooms to maintain their pleasantly firm, chewy texture over a wide range of cooking times. We prove it in this experiment by comparing how mushrooms’ texture changes with cooking compared to those of beef and zucchini.

Raw mushrooms are veritable sponges that can soak up a tremendous amount of oil. That’s because their stems and caps contain numerous air pockets in which oil can collect. However, cooking causes these air pockets to collapse and the mushrooms to shrink, which dramatically limits their ability to absorb oil as well as the amount of surface area to which the oil can cling. In fact, when we compared the oil absorption between equal weights of raw and precooked (microwaved so that they quickly exuded moisture) mushrooms, the raw batch absorbed a whopping 21 times more oil than the cooked sample. 

Mushrooms play a starring role in a variety of dishes—from soups, stews, and sauces to sautés, eggs, pastas, and savory tarts. Here are a few of our favorites.