Smell

The chemistry and meaning of mushroom aromas

A mushroom's smell comes from complex volatile organic compounds (secondary metabolites) released by the mycelium or fruiting body. M.Ya. Zerova notes in her «Key to the Fungi of Ukraine» that these substances evolved to attract insects (which spread the spores, as with the stinkhorn) or to repel grazing animals.

David Arora devotes a whole large section of «Mushrooms Demystified» to smells, stressing their phenomenal variety. Mushrooms can smell of anise, flour, garlic, radish, almond, rotting cabbage and even phenol (a pharmacy). Arora insists that in some genera (for example, Agaricus or webcaps — Cortinarius) identifying a species is simply impossible without assessing the smell.

For example, Roger Phillips in his guide «Mushrooms» describes a classic mistake when picking Agaricus mushrooms. The poisonous yellow stainer (Agaricus xanthodermus) looks just like an ordinary edible field mushroom. But if you sniff the base of its stem, you'll notice a sharp, unpleasant chemical smell of phenol (ink or carbolic), which grows stronger when cooked. Edible Agaricus mushrooms, meanwhile, smell pleasant — of anise or almond.

How to smell a mushroom properly

To catch a mushroom's true smell, simply holding it up to your nose isn't enough. Mycologists use special techniques:

1. Break or rub: The highest concentration of volatile compounds is released when cells are damaged. Break the cap, rub a piece of flesh or gills between your fingers and sniff right away.

2. Stem base: In many mushrooms (Agaricus in particular), the distinctive smell is most concentrated in the bulb at the very base of the stem.

3. Closed-container trick: If the smell is faint, put the mushroom in a closed plastic container or jar for 10-15 minutes. When you open the lid, the aroma will be at its strongest.

4. Heat test: Some smells (phenolic, for example) intensify sharply on contact with hot water.