Edibility class

Conditionally edible

In a mycologist's vocabulary, "conditionally edible" is one of the most common terms. To beginners it often sounds scary, but in fact a huge number of beloved traditional mushrooms (honey fungus, milk caps, lurid boletes) belong to exactly this category.

24 species in the database.

What does "conditionally" mean?

In the "Key to the Fungi of Ukraine", M.Ya. Zerova explains that conditionally edible mushrooms, when raw, contain water-soluble toxins, hemolytic poisons or very acrid, bitter resins (milky latex). If you simply fry such a mushroom, it will cause serious poisoning or be unbearably bitter.

However, these toxins and resins are unstable. They are completely destroyed or washed out by proper heat or cold processing. The condition for their safety is strict adherence to the preparation method.

Two main ways to make them safe

David Arora and Roger Phillips describe two main methods of preparing conditionally edible mushrooms:

This method is used to destroy thermolabile (heat-sensitive) poisons and water-soluble irritants.

- How it's done: The mushrooms are boiled for 15–20 minutes. The water (broth) MUST be poured away, because all the poisons have passed into it. The mushrooms themselves are rinsed in cold water. After that they become completely safe and can be fried, added to soup or pickled.

- Which mushrooms: Honey fungus (Armillaria mellea), Lurid boletes (Suillellus luridus), Wood blewits. False morels (Gyromitra) don't belong here: they are poisonous, their gyromitrin damages the liver and nervous system, and boiling doesn't guarantee safety — see the False morel page for details.

This method is used for mushrooms that contain hot, acrid milk.

- How it's done: The mushrooms are soaked in cold water for 2–3 days, changing the water regularly (every 8 hours). Then they are salted (often by the cold method), and through lactic acid fermentation the bitterness disappears completely over 30–40 days.

- Which mushrooms: Most species of the milk cap genus (Lactarius): white milk caps, woolly milk caps, ugly milk caps (Lactarius turpis).

Questions and answers

What if I boil a lurid bolete but don't pour off the first water, and make soup with it instead?

You will get severe gastrointestinal poisoning. The whole point of the procedure is to destroy the toxins with heat and wash the remains out into the broth. Pouring off the "first water" is the golden rule for conditionally edible mushrooms.

Why are milk caps considered poisonous in the West?

North America and Western Europe have no tradition of soaking and fermenting mushrooms for weeks (people there prefer button mushrooms, which can be fried right away). So their guides label acrid milk caps as "inedible" or "poisonous". In Eastern Europe, though, salting milk caps is a centuries-old cultural norm, so for us they are "conditionally edible" delicacies.

Can you eat raw honey fungus?

Never. Raw (or undercooked), the popular honey fungus contains substances that cause severe digestive upset and allergic reactions. It must be boiled first for at least 15-20 minutes.

Sources

1.Зерова М.Я. та ін. Визначник грибів України. 1979
2.Roger Phillips. Mushrooms (Roger Phillips)
3.David Arora. Mushrooms Demystified
4.Index Fungorum