Wild Mushrooms Are Cooked, Not Raw

Two things are true at once and they get conflated constantly.

Several well-known edible mushrooms are toxic raw and safe cooked. Cooking is a genuine and necessary step.

Cooking does nothing for the mushrooms that kill people. Amatoxins survive cooking, drying, freezing and every other kitchen process intact.

So cooking is required, and it is not a safety net.

The ones that are toxic raw

Morels. Genuinely toxic raw — they contain hydrazine compounds and haemolysins that cooking destroys. Raw morel poisoning is well documented and unpleasant. Cook thoroughly, and do not drink alcohol heavily with them, which has been associated with reactions.

Honey fungus. Must be well cooked, and it still causes gastric upset in a substantial minority of people who prepare it correctly. Start with a small amount.

Shaggy parasol. Reactions in some people even when cooked; a first try should be small.

Many boletes. Several are unpleasant raw and fine cooked.

Oyster mushrooms and most cultivated species. Better cooked, and shop mushrooms are no exception — common button mushrooms contain agaritine, which cooking reduces.

The general rule that follows: no wild mushroom is eaten raw. There is no upside and there are several downsides.

What cooking does not do

Amatoxins — death cap, destroying angel, deadly galerina — are heat-stable and completely unaffected. Boiling, frying, drying and freezing all leave them intact. Cases exist of poisoning from mushrooms dried and stored for months.

Orellanine, in some Cortinarius species, is likewise unaffected, and its latency of up to three weeks makes it particularly insidious.

Gyromitrin, in false morels, is partly removed by repeated parboiling with the water discarded — and unreliably so, and the vapour is itself hazardous. Poisonings continue among people following traditional preparation.

Coprine, in the common ink cap, is unaffected. The reaction with alcohol happens regardless of how the mushroom was cooked — which ink cap is which.

The delayed-onset toxins are precisely the ones cooking does not touch, which is the pattern set out in why the delay matters.

Practical rules

Cook thoroughly. Not a quick flash in a hot pan. Wild mushrooms want a proper sauté until the water has come out and gone again.

Try a small amount first, with a new species, and wait a day. Individual sensitivity varies substantially and is not predictable. Eat only one new species at a time, so that a reaction can be attributed.

Keep a specimen of anything you eat, uncooked, in the fridge for 48 hours. If someone becomes ill, that specimen is what allows identification, and identification changes treatment.

Do not drink heavily with a new species. Alcohol interacts with several, and it also confuses the picture if something goes wrong.

Do not feed wild mushrooms to children, pregnant women, elderly people or anyone immunocompromised on a first try.

Do not mix a foraged collection into a dish without having identified every specimen individually. One misidentified mushroom in a pan contaminates the whole dish.

Storage

• Paper bags, not plastic. Plastic sweats and turns a collection to mush.
• Refrigerate and use within a couple of days for most species.
• Ink caps are the exception and must be cooked within hours — they dissolve.
• Drying works well for many species and concentrates the flavour. It does not reduce toxicity.
• Freeze cooked rather than raw for most species.

The thing that is not a rule

There is no test, no preparation and no rule of thumb that makes an unidentified mushroom safe. Not cooking, not peeling, not soaking, not boiling and discarding the water, not silver spoons, not whether insects have been eating it.

Identification is done species by species, on the features in the parts of a mushroom, and confirmed with a spore print. The kitchen comes after that, and it never substitutes for it.

If the identification is not certain, the mushroom is not food. That is the whole of the safety advice, and every other consideration on this page assumes it has already been satisfied.