The name “chestnut mushroom” is applied to several different, mostly unrelated species, but today we’re discussing the one that goes by the scientific name, Philiota adiposa[i][ii]. Like many other philiotas, this one is a golden color with a scaly cap—the whole group is sometimes referred to as the scalycaps. This is a difficult group for foragers, in part because definite identification to species requires a microscope[iii], so cultivation may be the better bet.
In fact, for American mycophages (that is, fungus-eaters), cultivation may be the only option. Although some sources list it as occurring in North America as well as Europe, most describe it as a European species only. There are many American species that were initially given the names of European look-alikes by mistake, and this may be another such case.
Chestnut mushrooms are related to the Japanese Nameko and are popular gourmet mushrooms at the moment—which means there are a lot of articles about them online at the moment, not all of which make a whole lot of sense. Please exercise caution when doing your research. Also, note that there are poisonous Pholiotas, so please do not eat a wild mushroom just because it looks a bit like this one.
Agaricus adiposus Batsch,
Elench. fung. cont. prim. (Halle): 147 (1786)
Dryophila adiposa (Batsch) Quél.
Enchir. fung. (Paris): 68 (1886)
Hypodendrum adiposum (Batsch) Overh.
Identification & Description
Cap: 4-10 cm diameter, hemispherical with involute margin when young, expanding to convex, finally flattened with deflexed margin, with or without blunt umbo, not hygrophanous, not transculently striate, yellow-brown, with yellow to sulphur yellow marginal zone, entirely covered with apressed to uplifted, reddish to blackish brown, gelatinous squamules, particularly at center, in moist condition usually strongly slimy to glutinous, but slime easily washed off in rainy weather; when young with large velar flocks, especially at margin.
Gills: moderately crowded to crowded, broadly adnate, sometimes emarginate or with decurrent tooth, thin, subventricose, up to 10 mm broad, pale lemon-yellow at first, through ochre-brown to reddish brown with slight olivaceous tinge, with entire, concolorous edge.
Stem: 2-5 cm long x 0.5-1.0 cm diameter, centrally or slightly eccentrically inserted, tapering towards common base, solid then fistullose, when young with well-developed, thick, fibrillose-floccose annulus, above annulus pale yellow, orange to reddish brown below, glabrous above annulus, squamulose with dark reddish to blackish brown, gelatinous squamules below, glabrous above annulus.
Odor: indistinct, according to Bas et al. However, some older research has suggested that odor may be used as a defining characteristic for this species (Badcock, 1939).
Spore print: dark reddish brown.
Spores: 5-6.5 x 3-4 µm, smooth, ellipsoid, nonamyloid, amygdaliform. Further details on spore characteristics may be found in Batko (1946).
Habitat: found on living and dead stems of Fagus sylvatica, usually low on the stem or on roots and trunks; late summer to autumn; infrequent or rare.
Methanol extracts of P. adiposa fruit bodies were shown to inhibit the enzyme β-hydroxy-β-methyl glutaryl coenzyme a reductase (HMG-CoA reductase), a rate-limiting enzyme in cholesterol biosynthesis, by 55.8%. Solvent extraction and column chromatography were used to obtain a purified product, identified as stigmasterol, that had an IC50 of 6.8 µg (Yu et al., 2007).
The nutritive value of protein from the fruitbodies and the cultured mycelia of P. adiposa has been evaluated (Hui et al., 2004). Proteins from cultured mycelia had a higher nutritive value than from the fruitbodies, based on the following quantitative characteristics of protein quality:
- amino acid score 82.86
- chemical score 54.96
- essential amino acid index 92.73
- biological value 89.38
- nutritional index 35.42
- score of ratio coefficient of amino acid 87.24
The authors conclude that the submerged cultivated mycelium of P. adiposa could be considered a good source of protein.
Spiroaxanes are sesquiterpenes with a spiro[1,5]decane ring system; the canonical spiroaxane is shown below. These compounds have been isolated from a variety of marine sponges. Recently, a novel spiroaxane (15-hydroxy-6α,12-epoxy-7β, 10α H,11βH-spiroax-4-ene) was isolated from the culture broth of P. adiposa (Liu et al., 2008).
A variety of compounds have been isolated and purified from P. adiposa using column chromatography and and variety of spectroscopic techniques, including:
- 1-(N,N,N-trimethyl ethyl amino phosphoryl)-2,3-dilinolein ion
- glyceryl phosphate
Polysaccharides extracted from the mycelial culture of P. adiposa and administered intraperitoneally into white mice at a dosage of 300 mg/kg inhibited the growth of Sarcoma 180 and Ehrlich solid cancers by 70% and 60%, respectively (Ohtsuka et al., 1973).
The antitumor potential of P. adiposa was later corroborated in a Korean study using an antitumor screening test involving Sarcoma 180 cells transplanted into mice. Mice which were injected with a million Sarcoma 180 cells, and then one day later injected with the alcohol-precipitated polysaccharides from a hot-water extract of the fat Pholiota (at a dose of 20 mg/kg body weight per day for 10 days) had an inhibition ratio of 27.3%, compared to the mice that didn’t get the mushroom extract (Chung et al., 1982). Furthermore, it has been shown that treatment of Sarcoma 180 tumor-bearing mice with P. adiposa polysaccharides resulted in decreased tumor weights, increased carbon particle clearance and phagocytic indices, and significantly higher serum levels of TNF-α and IL-2, compared with untreated controls. The authors suggest that the anti-tumor activity of P. adiposa polysaccharide is related to immune system enhancement (Zhao et al., 2007)
The 60% methanolic extract of Pholiota adiposa exhibited antimicrobial activity, shown by using both the disc-diffusion and broth dilution methods (Dulger et al., 2004). Specifically, the extract (at 25 mg/ml) inhibited the growth of Bacillus subtilis (17.0/7.0/1.25), Escherichia coli (19.0/28.2/0.625), Klebsiella pneumonia (11.8/22.4/5.0), Staphylococcus aureus (18.6/19.8/1.25), Streptococcus pyogenes (11.0/18.0/2.5), and Mycobacteria smegmatis (20.4/16.0/0.625); the three numbers in parentheses indicate the zone of inhibition (mm), the zone of inhibition of the control antibiotic Gentamicin at 2 mg/ml, and the minimum inhibitory concentration (mg/ml).
Angiotensin I-converting enzyme (ACE) inhibitors have shown utility in relieving or preventing hypertension. P. adiposa was shown to inhibit angiotensin I-converting enzyme (ACE) (Izawa et al., 2006). Also, an ACE inhibitor, identified as a novel pentapeptide (amino acid sequence Gly-Glu-Gly-Gly-Pro) was isolated from the fruiting body of Pholiotoa adiposa. Maximal ACE inhibitory activity (IC50; 0.25 mg) was obtained with a protracted warm water extraction (30°C for 12h); after extensive purification, this activity increased to an IC50 of 0.044 mg (Koo et al., 2006).
Researchers used a combination of the herb Lycii fructus and P. adiposa to produce a traditional Korean rice wine with antihypertensive properties (Kim et al., 2006). The addition of 1% L. fructus and 0.1% P. adiposa fruiting bodies into the mash prior to fermentation produced a wine which had an antihypertensive ACE inhibitory activity of 82%.
Investigating the effect of a P. adiposa extract on fat mass in hyperlipidemic mice on a high-fat diet, one study concluded this mushroom may have potential for use as a functional food that can act as a prophylactic against hyperlipidemia. Although the extracts did not cause any significant change in the total triglyceride contents nor the epididymal fat mass, the retroperitoneal fat decreased significantly decreased in mice on the high-fat diet (Cho et al., 2006). Excessive retroperitoneal fat mass is typical in males with upper-body obesity (Arner, 1997).
Growing Chestnut Mushrooms
You may be able to find chestnut mushrooms at a farmer’s market or in specialty grocery stores, but that’s rare. Cultivation may be the only way most Americans (and most Europeans who don’t have a high-end microscope) can get access to this species. You can buy pre-inoculated grow-kits from various suppliers[i]. These will come with instructions and are more or less straight-forward.
Alternatively, you can buy live culture[ii]. Stabilize your culture on agar, then inoculate either your own grow logs (it likes beech best) or, for indoor-growing, incubate it on grain, then transfer it to enriched sawdust or straw to fruit. Indoor grows are definitely much faster but more labor-intensive. Temperature and humidity requirements vary throughout the growing process, but temperature should normally be low, mostly in the sixties (please consult an experienced grower for details). Even indoors, Chestnut Mushroom is slower than many other cultivated species. The mycelium can sometimes become yellow or yellowish, so don’t mistake the color change for contamination.
Chestnut mushroom is difficult to clone from fruiting body fragments. We have not been able to track down information on starting from spores.
Chestnut mushrooms are best harvested slightly premature, as the stems can become tough with age. Growing outdoors on logs is really best done in the species’ home-range, in Europe. Otherwise take careful steps to prevent the fungus from escaping into the wild in places where it doesn’t belong.
Cooking and Eating Chestnut Mushrooms
Reportedly, Chestnut Mushrooms have a nutty taste and a chewy texture that holds up well to cooking. Shitakes, which are much easier to find in stores, are quite similar. The mushrooms do not contain much nutrition—a definite advantage for people who enjoy eating but want to lose weight. A hundred-gram serving contains only 15 calories and is not an important source of protein, fats, or carbohydrates. The mushroom does provide some niacin and some pantothenic acid, though[i].
Chestnut mushrooms do very well in Japanese-style noodle dishes. They—or especially the long stems—are good roasted with onions[ii].
Chestnut Mushroom Toxicity, Safety & Side Effects
At least one reliable source recommends against eating chestnut mushroom without saying why. Since that source is based in the UK where this species grows wild, it seems likely their concern has to do with foragers misidentifying the species and picking a poisonous Pholiota instead. There are also other species in the genus that are not-uncommonly eaten but are of questionable safety. It seems reasonable to exercise some caution with this species, but that is true of many commonly-eaten mushrooms.
Given the danger of misidentification, though, it does seem best not to collect wild-growing specimens for the table, especially if you find something that looks like Chestnut Mushroom growing wild in North America
[i] (n.d.). Pholiota adiposa (Batsch) P. Krumm. First Nature
[ii] Bergo, A. (2023). The Chestnut Mushroom. Forager-Chef
[iii] Kuo, M. (2007). The Genus Pholiota. MushroomExpert
[iv] Bergo, A. (2023). The Chestnut Mushroom. Forager-Chef
[v] (2022). How to Grow Chestnut Mushrooms. Fungi Academy
[vi] (n.d.) Pholiota adiposa. CalorieSlism
[vii] Bergo, A. (2023). The Chestnut Mushroom. Forager-Chef
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