Smell

Unpleasant

"Unpleasant smell" is a broad category in mycology that covers many repulsive scents: from old rags and rotten cabbage to bleach, coal gas and spoiled potatoes. The most important rule in mycology is that an unpleasant smell is almost always a warning sign.

2 species in the database.

Unpleasant smells as an indicator of toxicity

M.Ya. Zerova in the "Key to the Fungi of Ukraine" emphasizes that evolution often (though not always) uses sharp, repulsive smells to warn animals that the fruiting body contains toxins.

David Arora in "Mushrooms Demystified" gives vivid examples of mushrooms whose unpleasant smell has become legendary:

1. Destroying angel (Amanita virosa): This snow-white, deadly poisonous mushroom got its Ukrainian name ("stinking amanita") from its heavy, stifling smell, compared to damp cellars, spoiled potatoes or a hint of bleach. This is the main feature that sets it apart from Agaricus mushrooms.

2. Sulfur knight (Tricholoma sulphureum): A poisonous yellow mushroom with an extremely sharp and repulsive smell of coal (lighting) gas, carbide or tar. It cannot be mistaken for the pleasant smell of the edible Yellow knight.

3. Gymnopus brassicolens: A small forest mushroom with a powerful smell of rotten or overripe cabbage.

Roger Phillips warns that an unpleasant smell also often appears in overripe specimens of edible mushrooms, a sign that rotting has begun and cadaveric poisons (ptomaines) are building up.

Specific "unpleasant" smells

Instead of one general word, "unpleasant", experienced foragers tell the nuances apart:

- Smell of dust/mold: Often typical of poisonous fibrecaps (Inocybe).

- Smell of rubber or burnt horn: Found in some inedible polypores and bonnets (Mycena).

- Smell of ammonia (urine): Some puffballs in old age, or mushrooms growing on dung, can have a sharp ammonia smell.

Questions and answers

If a mushroom smells pleasant, is it definitely safe?

No! This is the most important rule to remember: an unpleasant smell means "don't eat", but a pleasant smell does NOT mean "safe to eat". A young death cap smells pleasant (a sweet, mushroomy smell).

Can you boil a bad-smelling mushroom to make it edible?

No. Boiling (even for a long time) poisonous mushrooms such as the Sulfur knight or the Destroying angel will destroy the volatile compounds (the smell will go away), but it will not break down the heavy toxins (amatoxins), which will stay in the flesh and the cooking water.

Why do some edible mushrooms smell unpleasant too?

It is rare, but it happens. For example, some oyster mushrooms (Pleurotus) can have a slight "fishy" or "rag-like" smell in wet weather. The edible Common stinkhorn also smells of rotting flesh when mature, but it simply is not eaten at that stage.

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