R. G. Benedict & D. E. Stuntz Pacific Search, September 1975
The far‑roaming pothunter may encounter 27 different odors in fresh mushrooms that grow in the Pacific Northwest. In the words of Jimmy Durante, “The nose knows!”
The keys and descriptions in the average mushroom field book tell little or nothing about the characteristic odors of certain mushrooms that could give additional clues to their identity.
Sometimes a specimen contains only traces of the chemicals responsible for its aroma. You need to split or cut the fresh mushroom and immediately smell the inner cut portions. Carry notepaper with you on which to record any odor you may detect, along with other identifying features, and insert this record in the collection sack with the specimens.
Though odor perception and definitions vary widely among individuals, mushroom odors are arbitrarily divided into three groups: pleasant, neutral, and unpleasant. Although there should be no disagreement within the “pleasant odor” group, some readers undoubtedly would shift some of the neutral odors to “unpleasant” or vice versa.
Odors in mushrooms usually arise from volatile essential oils that contain mixtures of chemicals like esters, aldehydes, ketones, and amines. A simple example of a pleasant‑smelling compound is ethyl butyrate, the odor of pineapple. Examples of aldehydes are compounds like formaldehyde and acetaldehyde, which give off pungent, unpleasant smells. In some cases more than one chemical in the same group, or representative chemicals of more than one group (e.g., both esters and aldehydes), may contribute to the combination.
Amines always contain the element nitrogen. The simplest organic one is methylamine. This substance has a smell similar to, but more unpleasant than, household ammonia.
We begin with the pleasant aromas and, where known, provide an indication of some of the chemical compounds involved. Edible mushrooms with the pleasant aroma of almond extract are Phaeolepiota aurea, Hygrophorus bakerensis, H. agathosmus, and Agaricus sylvicola. Non‑edible fungi with similar odor are Russula laurocerasi and R. foetens. The odor of R. foetens changes as the mushroom ages and becomes extremely disagreeable, in fact, nauseating. Almond‑extract odor probably results from a combination of chemicals that include benzaldehyde and close relatives.
Several species of mushrooms, none of which have culinary interest, exude a fragrant or sweet odor. Among the spine fungi, the sweet smell of Hydnellum peckii helps to set it apart from related species. Clitocybe morganii and Mycena odora bear a tutti‑frutti chewing gum smell. Burnt sugar is a rare scent in the fleshy fungi, but is well documented in Hebeloma sacchariolens.
The spicy fragrance of Lactarius helvus, only rarely found on the Pacific coast, is an odd combination of cinnamon and gunpowder smoke. The distinctive smell of Pholiota squarrosoides, a wood‑inhabiting fungus, recalls cinnamon buns. Without doubt an analytical chemist could extract cinnamaldehyde or cinnamic acid from this fungus.
Grape soda pop aroma has been noted only in Squamanita odorata and Clitocybe clavata, the grape clitocybe. Japanese forms of C. clavata have been known to cause illness when an alcoholic beverage is consumed with the mushroom. The aroma of specimens in our region is probably due to methylanthranilate, the compound used to prepare synthetic grape flavor.
Most common of the pleasant aromas is anise oil. It occurs in Agaricus augustus, A. pusillus, A. micromegethus, A. niveus, Clitocybe odora, and C. suveolens. Some of the tough, woody fungi of the genus Lentinus also give off this pleasant smell. A well‑known representative of this genus is L. lepideus which grows on dead stumps and logs in fall. Anise oil contains anethole. It is sometimes used in pharmacy as a laxative, frequently combined with licorice.
Fruity aromas, uncommon in fleshy fungi, are best represented by pear and apricot. The fragrance of pear is found in Inocybe pyriodora, Cortinarius traganus, and C. fragrans. An apricot‑like scent emanates from Cantharellus cibarius, the popular yellow chanterelle.
Lactarius camphoratus, an uncommon mushroom in this area, has the sweet aromatic odor of fenugreek. A legume, native to Europe, produces these seeds, which serve as an ingredient in curry powder and in artificial maple flavoring.
The subtle, aromatic odor of Armillaria ponderosa [=Tricholoma magnivelare] and A. caligata is reminiscent of tincture of benzoin. Benzoin is a dry, brittle, fragrant resin from certain plants that grow in Java and Sumatra. It is used in perfumes and medicines. Local mushroom hunters refer to this odor as the “matsutake odor” or pine scent. (“Matsutake” is the Japanese name for A. ponderosa.) Chemical compounds isolated from the Japanese matsutake are methyl cinnamate and matsutake alcohol.
Many fleshy fungi have no characteristic odor. Others have a difficult‑to‑define combination of light but pleasant aromas, often referred to as the typical mushroom odor. Familiar specimens of this type are Collybia dryophila, Flammulina velutipes, Lepista nuda, and the Agaricus bisporus that you find in your favorite supermarket’s produce section.
The pronounced smell of green corn, not yet chemically defined, occurs in the poisonous Inocybe sororia and Inocybe species #3399. It is also detected in Cortinarius superbus and Cystoderma amianthinum.
Few species of amanitas have telltale aromas, but one with a sprouting‑potato odor is Amanita porphyria, a non‑edible form. The chances of picking a white‑gilled, white‑spored, potato‑scented, mushroom that is not A. porphyria are rare. Mushrooms with similar odor are Volvariella speciosa and Pluteus cervinus. Both have pink gills and spores, but P. cervinus lacks a volva at the base of the stem.
Cucumber, farinaceous, and rancid‑linseed‑oil odors are found in numerous mushrooms. The main difference between these three odors is that of intensity. The mild odor of cucumber is revealed in Galerina marginata, G. autumnalis, G. venenata, and Phaeocollybia kauffmanii. A farinaceous smell, often expressed as “mealy” or “branny,” is attributed to Tricholoma flavovirens, Entoloma lividum, and E. sericeum. The strong odor of rancid linseed oil is highly noticeable in Armillaria zelleri, Tricholoma pessundatum, T. vaccinum, T. populinum, and Clitocybe sinopica. An interesting but uncommon smell, somewhat like tincture of iodine, is known as iodoform. It describes the scent from non‑edible Polyporus hirtus and Mycena iodiolens. Tricholoma saponaceum, a common mushroom of low quality for the pot, has a soapy odor.
Among the unpleasant odors, categories of fishy, spoiled hamburger, and chestnut catkins are much alike and occur primarily in species of the large, poisonous genus Inocybe. Common examples are I. pudica and I. napipes. Similar odors appear in Verpa bohemica and the Morchella species. The edible Russula xerampelina smells like shrimp. Pothunters say that the odor from cooking this species will drive you out of the kitchen, and recommend it be cooked outdoors. These odors result from simple amines like methyl, ethyl, and propyl amine.
Mushrooms in the Amanita solitaria and A. chlorinosma groups often smell like chlorine household bleach (sodium hypochlorite). Skunk cabbage is a rare aroma in this region’s fungi, but is unmistakable in Clitocybe nebularis and C. alba.
Several species of Marasmius have chemicals similar to those in garlic. One small carpophore of M. scorodonius, M. prasiosmus, or M. foetidum could add considerable flavor to a pot roast. Oil of garlic is allyl sulphide.
Acetylene, a flammable gas, is almost odorless when pure. Commercial acetylene, made by adding water to calcium carbide, contains impurities that give it an odor similar to garlic. Certain basidiomycetes contain antibiotic substances which inhibit the growth of bacteria or fungi. One such antibiotic is Diatretyn I, found in Clitocybe diatreta. Some of these chemicals are unstable and release acetylene when they decompose. The sharp orders of Clitocybe inversa and Ripartites helomorpha, especially when wet, are probably due to the decomposition of polyacetylenic compounds present.
Hebeloma crustuliniforme and H. mesophaeum possess a nauseous combination of radish and the odious organic solvent, pyridine. The pretty, lavender‑colored Mycena pura and the hallucinogenic Psilocybe cyanescens have a mild radish scent.
As coal is converted to coke, the coal gas vapors contain many odious chemicals in addition to odor‑free methane and hydrogen gases. Mushroom scents arising from Tricholoma inamoenum, T. sulphureum, and Lepiota bucknallii are said to resemble those in the unpurified mixture of vapors.
Stinkhorns are highly specialized fleshy fungi with the nauseating odors of decaying flesh. They are so strong to the nose that one can detect their presence 50 feet downwind. Although they are rare west of the Cascades, one occasionally encounters Mutinus caninus and, rarely, Lysurus gardneri. The stench odors arise from fly‑attracting aldehydes not commonly encountered in chemistry. One such compound is phenylacetaldehyde, isolated from Phallus impudicus.
Agaricus placomyces and A. hondensis have a phenol or creosote odor. Violent gastronomic upsets await anyone foolish enough to eat the odorous forms of these fungi.
When certain species of Mycena are crushed between thumb and forefinger, the distinctive odor of nitrous acid or fuming nitric acid can be detected.
In many species of mushrooms, including Marasmius oreades, the odor of hydrogen cyanide can be detected.
Perhaps this article will stimulate those pothunters who have not done so in the past to make better use of their olfactory faculties. There is no rule of thumb regarding mushroom odors, but in practically all cases, either the unpleasant‑smelling specimens have odors which are not dissipated upon cooking, or the mushrooms are poisonous, or both. In one incident, a woman suffered muscarinic poisoning when she ate some specimens not described in the 1962 publication of the book The Savory Wild Mushroom (revised and enlarged in 1971). These turned out to be Inocybe pudica, and had she taken the time to smell them first we doubt if she would have been tempted.
DR. STUNTZ was a professor of botany at the University of Washington and scientific advisor to the Puget Sound Mycological Society. DR. BENEDICT, a semi‑retired microbiologist, was formerly a research associate professor of pharmacognosy in the University of Washington School of Pharmacy.
