Boletus edulis
Encyclopedia
Boletus edulis, commonly
known as penny bun, porcino or cep, is a basidiomycete fungus, and the type species
of the genus Boletus
. Widely distributed in the Northern Hemisphere
across Europe
, Asia
, and North America
, it does not occur naturally in the Southern Hemisphere, although it has been introduced
to southern Africa
, Australia
and New Zealand
. Several closely related European mushrooms formerly thought to be varieties or forms
of B. edulis have been shown using molecular phylogenetic analysis to be distinct species, and others previously classed as separate species are conspecific with this species. The western North American species commonly known as the California king bolete (Boletus edulis var. grandedulis) is a large, darker-coloured variant that was first formally identified in 2007.
The fungus grows in deciduous and coniferous forests and tree plantations, forming symbiotic ectomycorrhizal
associations with living trees by enveloping the tree's underground roots with sheaths of fungal tissue. The fungus produces spore
-bearing fruit bodies above ground in summer and autumn. The fruit body has a large brown cap
which on occasion can reach 35 cm (14 in) in diameter and 3 kg (6.6 lb) in weight. Like other bolete
s, it has tubes extending downward from the underside of the cap, rather than gills; spores escape at maturity through the tube openings, or pores. The pore surface of the B. edulis fruit body is whitish when young, but ages to a greenish-yellow. The stout stipe
, or stem, is white or yellowish in colour, up to 25 cm (10 in) tall and 10 cm (3.9 in) thick, and partially covered with a raised network pattern, or reticulations.
Prized as an ingredient in various foods, B. edulis is an edible mushroom
held in high regard in many cuisines, and is commonly prepared and eaten in soups, pasta
, or risotto
. The mushroom is low in fat
and digestible carbohydrate
s, and high in protein, vitamin
s, mineral
s and dietary fibre. Although it is sold commercially, it has not been successfully grown in cultivation. Available fresh in autumn in Central
, Southern
and Northern Europe
, it is most often dried, packaged and distributed worldwide. Keeping its flavour after drying, it is then reconstituted and used in cooking. Boletus edulis is one of the few fungi that are sold pickled. The fungus also produces a variety of organic compound
s with a diverse spectrum of biological activity
, including the steroid derivative ergosterol
, a sugar binding protein
, antiviral
compounds, antioxidant
s, and phytochelatin
s, which give the organism resistance to toxic heavy metals.
Boletus edulis was first described
in 1782 by the French botanist Pierre Bulliard
and still bears its original name. The starting date of fungal taxonomy
had been set as January 1, 1821, to coincide with the date of the works of the 'father of mycology', Swedish naturalist Elias Magnus Fries
, which meant that the name required sanction by Fries (indicated in the name by a colon) to be considered valid, as Bulliard's work preceded this date. It was thus written Boletus edulis Bull.:Fr. However, a 1987 revision of the International Code of Botanical Nomenclature set the starting date at May 1, 1753, the date of publication of Linnaeus' seminal work, the Species Plantarum
. Hence the name no longer requires the ratification of Fries' authority. Early alternate names
include Boletus solidus by English naturalist James Sowerby
in 1809, and Gray's
Leccinum edule. Gray's transfer of the species to Leccinum was later determined to be inconsistent with the rules of botanical nomenclature
, and it is apparent that he was unfamiliar with the earlier works of Fries when he published his arrangement of bolete species.
Boletus edulis is the type species
of the genus Boletus
. In Rolf Singer
's classification
of the Agaricales
mushrooms, it is also the type species of section Boletus, a grouping of about 30 related boletes united by a number of characteristics: a mild-tasting white flesh
that does not change colour when exposed to air; a smooth to distinctly raised netted pattern over at least the uppermost portion of the stem; a yellow-brown or olive-brown spore print
; white tubes that later become yellowish then greenish, and that initially appear to be stuffed with cotton; and cystidia that are not strongly coloured. Molecular analysis published in 2006 established that the bolete mushrooms are all derived from a common ancestor
, and established the Boletales
as an order
separate from the Agaricales.
The first named species of the genus Boletus
, the generic
name is derived from the Latin
term bōlētus "mushroom", which was borrowed in turn from the Ancient Greek
βωλίτης, "terrestrial fungus". Ultimately, this last word derives from bōlos/βῶλος "lump", "clod", and, metaphorically, "mushroom". However, the βωλίτης of Galen
, like the boletus of Latin writers like Martial
, Seneca
and Petronius
, is often identified as the much prized Amanita caesarea
. The specific epithet edulis in Latin means "eatable" or "edible".
s for Boletus edulis vary by region. The standard Italian name porcino means "piglet" in Italian
, and echoes the term suilli, literally 'hog mushrooms', used by the Ancient Romans, and still surviving in Southern Italian words for this mushroom. The derivation has been ascribed to the resemblance of young fruit bodies to piglets, or to the fondness pigs have for eating them. It is also known as king bolete. The English penny bun
refers to its rounded brownish shape. The German
name Steinpilz "stone mushroom" is derived from the firm flesh. In Austria it is called Herrenpilz, the "gentlemen's mushroom", while in Mexico, the Spanish
name is panza, meaning "belly". Another Spanish name, rodellon, means "small round boulder", while the Dutch
name eekhoorntjesbrood means "squirrel's bread". In Albanian
it is called pankushe or barkushe, the first name probably deriving from Latin
and the second one its analog in Albanian meaning "the belly one" from bark=belly. In Russia and some ex-Soviet republics
Boletus edulis is known as white mushroom (where "white" means "noble" as opposed to "black" i.e. common mushrooms). Its Polish
name prawdziwek stems from 'prawda' or truth, suggesting that it is the "true mushroom", reflecting its status as the king of field mushrooms in that country. In Montenegro, Bosnia and Herzegovina, Croatia and Serbia it is known as pravi vrganj (true vrganj), or more often only as vrganj, which is actually the common name for the whole Boletus genus.
The vernacular name cep is derived from the Catalan
cep or its French
name cèpe, although the latter is a generic term applying to several species. In France, it is more fully cèpe de Bordeaux, derived from the Gascon
cep "trunk" for its fat stalk, ultimately from the Latin
cippus "stake". Ceppatello, ceppatello buono, ceppatello bianco, giallo leonato, ghezzo, and moreccio are names from Italian dialects, and ciurenys or surenys is another term in Catalan. The French-born King Charles XIV John
popularised B. edulis in Sweden after 1818, and is honoured in the local vernacular name Karljohanssvamp. The monarch cultivated the fungus about his residence, Rosersberg Palace
. It is known as hed tab tao in Thai
.
of this mushroom is 7–30 cm (3–12 in) broad at maturity. Slightly sticky to touch, it is convex in shape when young and flattens with age. The colour is generally reddish-brown fading to white in areas near the margin, and continues to darken as it matures. The stipe
, or stem, is 8–25 cm (3.5–10 in) in height, and up to 7 cm (2.8 in) thick—rather large in comparison to the cap; it is club-shaped, or bulges out in the middle. It is finely reticulate on the upper portion, but smooth or irregularly ridged on the lower part. The under surface of the cap is made of thin tubes, the site of spore
production; they are 1 to 2 cm (0.393700787401575 to 0.78740157480315 in) deep, and whitish in colour when young, but mature to a greenish-yellow. The angular pores, which do not stain when bruised, are small — roughly 2 to 3 pores per millimetre. In youth the pores are white and appear as if stuffed with cotton (which is actually mycelia
); as they age, they change colour to yellow and later to brown. The spore print
is olive brown. The flesh
of the fruit body is white, thick and firm when young, but becomes somewhat spongy with age. When bruised or cut, it either does not change colour, or turns a very light brown. Fully mature specimens can weigh about 1 kg (2.2 lb); a huge specimen collected on the Isle of Skye, Scotland, in 1995 bore a cap of 42 cm (16.5 in), with a stipe 18 cm (7.1 in) in height and 14 cm (5.5 in) wide, and weighed 3.2 kg (7.1 lb).
Boletus edulis is considered one of the safest wild mushrooms to pick for the table, as there are no poisonous species that closely resemble it. The most similar mushroom may be the devil's bolete (Boletus satanas), which has a similar shape, but has a red stem and stains blue on bruising. However, it is often confused with the very bitter and unpalatable Tylopilus felleus
, but can be distinguished by the reticulation on the stalk; in porcini, it is a whitish net-like pattern on a brownish stalk, whereas it is a dark pattern on white in the latter. Porcini have whitish pores while the other has pink. If in doubt, tasting a tiny bit of flesh will yield a bitter taste. It can also resemble the "bolete-like" Gyroporus castaneus
, which is generally smaller, and has a browner stem.
The spores
are elliptical to spindle-shaped, with dimensions of 12–17 by 5–7 µm
. The basidia, the spore-bearing cells, are produced in a layer lining the tubes, and arrange themselves so their ends are facing the center of the tube; this layer of cells is known technically as a hymenium
. The basidia are thin-walled, mostly attached to 4 spores, and measure 25–30 by 8–10 µm. Another cell type present in the hymenium are the cystidia, larger sterile cells that protrude beyond the basidia into the lumen
of the hymenium, and act as air traps, regulating humidity. B. edulis has pleurocystidia (cystidia located on the face of a pore) that are thin-walled, roughly spindle-shaped to ventricose
, and measure 30–45 by 7–10 µm; the hymenium does not have cheilocystidia — cells found on the edges of the pores. The hypha
e of B. edulis do not have clamp connection
s.
Molecular phylogenetic analyses have proven that these three are all distinctive and separate species; other taxa formerly believed to be unique species or subspecies, such as B. betulicola, B. chippewaensis, B. persoonii, B. quercicola and B. venturii, are now known to be part of a B. edulis species complex
with a wide morphological
, ecological and geographic range, and that the genetic variability in this complex is low. Similar molecular technology has been developed to rapidly and accurately identify B. edulis and other commercially important fungi.
Western North America has a number of species closely related to B. edulis. The white king bolete (Boletus barrowsii
), found in parts of Colorado
, New Mexico
, Arizona
, and California
(and possibly elsewhere), is named after its discoverer Chuck Barrows. It is lighter in colour than B. edulis, having a cream-coloured cap with pink tones; often mycorrhizal with Ponderosa pine
, it tends to grow in areas where there is less rainfall. Some find its flavour as good as if not better than B. edulis. The California king bolete (Boletus edulis var. grandedulis) can reach massive proportions, and is distinguished from B. edulis by a mature pore surface that is brown to slightly reddish. The cap colour appears to be affected by the amount of light received during its development, and may range from white in young specimens grown under thick canopy, to dark-brown, red-brown or yellow brown in those specimens receiving more light. The queen bolete (Boletus regineus
), formerly considered a variety of B. aereus, is also a choice edible. It is generally smaller than B. edulis, and unlike that species, is typically found in mixed forests. The spring king bolete (Boletus rex-veris
), formerly considered a variety of B. edulis or B. pinophilus, is found throughout western North America. In contrast to B. edulis, B. rex-veris tends to fruit in clusters, and, as its common name suggests, appears in the spring.
spp.) and fir (Abies spp.) trees, although other hosts include chestnut
, chinquapin
, beech
, Keteleeria
spp., Lithocarpus
spp., and oak
. In California, porcini have been collected in a variety of forests, such as coastal forests, dry interior oak forests and savanna
s and interior high-elevation montane
mixed forests, to an altitude of 3,500 m (11,500 ft). In northwestern Spain, they are common in scrublands dominated by the rock rose
species Cistus ladanifer and Halimium lasianthum.
Boletus edulis has a cosmopolitan distribution
, concentrated in cool-temperate
to subtropical regions. It is common in Europe
—from northern Scandinavia, south to the extremities of Greece and Italy—and North America
, where its southern range extends as far south as Mexico. It is well known from the Borgotaro area of Parma
, Italy
, and has PGI
status there. The European distribution extends north to Scandinavia and south to southern Italy and Morocco. In China, the mushroom can be found from the northeastern Heilongjiang Province to the Yunnan-Guizhou Plateau and Tibet
. It has been recorded growing under Pinus and Tsuga in Sagarmatha National Park
in Nepal
, as well as in the India
n forests of Arunachal Pradesh
.
. It is often found underneath oak and silver birch in Hagley Park
in central Christchurch
, New Zealand
, where it is likely to have been introduced
, probably on the roots of container-grown beech, birch, and oak in the mid-19th century—around the time exotic trees began to be planted in the Christchurch area. It has been growing plentifully in association with pine forests in the southern KwaZulu-Natal Midlands
in South Africa for more than 50 years and is believed to have been introduced with the import of pine trees. It also grows in pine plantations in neighboring Zimbabwe.
appeared to have a negative effect on fruit body production, but previous studies reported contradictory results. A Lithuanian study conducted in 2001 concluded that the maximal daily growth rate of the cap (about 21 mm or 0.8 in) occurred when the relative air humidity was the greatest, and the fruit bodies ceased growing when the air humidity dropped below 40%. Factors most likely to inhibit the appearance of fruit bodies included prolonged drought, inadequate air and soil humidity, sudden decreases of night air temperatures, and the appearance of the first frost
. Plots facing north tend to produce more mushrooms compared to equivalent plots facing south.
l—it is in a mutualistic relationship with the roots of plants ("hosts"), in which the fungus exchanges mineral
s extracted from the environment for fixed carbon
from the host. Other benefits for the plant are evident: in the case of the Chinese Chestnut
, the formation of mycorrhizae with B. edulis increases the ability of plant seedlings to resist water stress
, and increases leaf succulence, leaf area, and water-holding ability. The fungus forms a sheath of tissue around terminal, nutrient-absorbing rootlets of the host, forming so-called "ectomycorrhizae"; the fungal hypha
e emanate throughout the soil, effectively increasing the surface area for nutrient absorption, and the fungus penetrates between cells of the cortex
to facilitate nutrient exchange. Compatible hosts may belong to multiple families of vascular plant
s that are widely distributed throughout the Northern Hemisphere; according to one 1995 estimate, there are at least 30 host plant species distributed over more than 15 genera. Examples of mycorrhizal associates include Chinese red pine
, Mexican weeping pine
, Scots pine, Norway spruce, Coast Douglas-fir, mountain pine, and Virginia pine. The fungus has also been shown to associate with Gum rockrose, a pioneer
early stage shrub that is adapted for growth in degraded areas, such as burned forests. These and other Rockrose
species are ecologically important as fungal reservoirs, maintaining an inoculum of mycorrhizal fungi for trees that appear later in the forest regrowth cycle
.
The mushroom has been noted to commonly co-occur with Amanita muscaria
or A. rubescens, although it is unclear whether this is due to a biological association between the species, or because of similarities in growing season, habitat, and ecological requirements. An association has also been reported between B. edulis and Amanita excelsa on Pinus radiata ectomycorrhizae in New Zealand, suggesting that other fungi may influence the life cycle of porcini. A 2007 field study revealed little correlation between the abundance of fruit bodies and presence of its mycelia below ground, even when soil samples were taken from directly beneath the mushroom; the study concluded "Factors triggering formation of mycorrhizae and fructification of porcini appear to be too complex to be simply explained on the basis of the amount of fungal mycelia in the soil."
. The mushroom's resistance to heavy metal toxicity is conferred by a biochemical called a phytochelatin
—an oligopeptide
whose production is induced after exposure to metal. Phytochelatins are chelating agents
, capable of forming multiple bonds with the metal; in this state, the metal cannot normally react with other elements or ions and is stored in a detoxified form in the mushroom tissue.
, known as the bolete eater, which manifests itself as a white, yellow, or reddish-brown cottony layer over the surface of the mushroom. Some reported cases of stomach ache
following consumption of dried porcini have been attributed to the presence of this mould on the fruit bodies. The mushroom is also used as a food source by several species of mushroom flies, as well as other insects and their larvae
. An unidentified species of virus
was reported to have infected specimens found in the Netherlands and in Italy; fruit bodies affected by the virus had relatively thick stems and small or no caps, leading to the name "little-cap disease".
Boletus edulis is a food source for animals such as the banana slug
(Ariolimax columbianus), the Long-haired Grass Mouse
, the Red Squirrel
, and, as noted in one isolated report, the Fox Sparrow
.
. Italian chef and restaurateur Antonio Carluccio
has described it as representing "the wild mushroom par excellence", and hails it as the most rewarding of all fungi in the kitchen for its taste and versatility. Considered a choice edible, particularly in France, Germany and Italy, it was widely written about by the Roman writers Pliny the Elder
and Martial
, although ranked below the esteemed Amanita caesarea
.
wrote the disgruntled Martial when served suilli instead of boleti. The term suilli was also thought to encompass the related Leccinum scabrum.
The flavour has been described as nutty and slightly meaty, with a smooth, creamy texture, and a distinctive aroma reminiscent of sourdough
. Young, small porcini are most appreciated by gourmets, as the large ones often harbor maggot
s (insect larvae), and become slimy, soft and less tasty with age. Fruit bodies are collected by holding the stipe near the base and twisting gently. Cutting the stipe with a knife may risk the part left behind rotting and the mycelium
being destroyed. Peeling and washing are not recommended. The fruit bodies are highly perishable
, due largely to the high water content (around 90%), the high level of enzyme
activity, and the presence of a flora of microorganisms. Caution should be exercised when collecting specimens from potentially polluted or contaminated
sites, as several studies have shown that the fruit bodies can bioaccumulate
toxic heavy metals like mercury
, cadmium
, caesium
and polonium
. Bioaccumulated metals or radioactive fission decay products
are like chemical signatures: chemical
and radiochemical
analysis can be used to identify the origin of imported specimens, and for long-term radioecological
monitoring of polluted areas.
Porcini are sold fresh in markets in summer and autumn in Central
and Southern Europe
, and dried or canned at other times of the year, and distributed worldwide to countries where they are not otherwise found. They are eaten and enjoyed raw, sautéed with butter, ground into pasta, in soups, and in many other dishes. In France, they are used in recipes such as cèpes à la Bordelaise, cèpe frits and cèpe aux tomates. Porcini risotto
is a traditional Italian autumn dish. Porcini are a feature of many cuisines, including Provençal
, and Viennese
. They are used in soups and consumed blanched in salads in Thailand
. Porcini can also be frozen — either raw or first cooked in butter. The colour, aroma, and taste of frozen porcini deteriorate noticeably if frozen longer than four months. Blanching or soaking and blanching as a processing step before freezing can extend the freezer life up to 12 months. They are also one of the few mushroom species pickled and sold commercially.
Boletus edulis is well suited to drying — its flavour intensifies, it is easily reconstituted, and its resulting texture is pleasant. Reconstitution is done by soaking in hot, but not boiling, water for about twenty minutes; the water used is infused with the mushroom aroma and it too can be used in subsequent cooking. Dried porcini have more protein than most other commonly consumed vegetables apart from soybean
s. However, some of this content is indigestible, though digestibility is improved with cooking.
Like other boletes, porcini can be dried by being strung separately on twine and hung close to the ceiling of a kitchen. Alternatively, the mushrooms can be dried by cleaning with a brush (washing is not recommended), and then placing them in a wicker basket or bamboo steamer
on top of a boiler or hot water tank. Another method is drying in an oven at 25 to 30 °C (77 to 86 F) for two to three hours, then increasing the temperature to 50 °C (122 °F) until crisp or brittle. Once dry, they are kept in an airtight jar. Importantly for commercial production, porcini retain their flavour after industrial preparation in a pressure cooker
or after canning or bottling, and are thus useful for manufacturers of soups or stews. The addition of a few pieces of dried porcino can significantly add to flavour, and they are a major ingredient of the pasta sauce known as carrettiere (carter's sauce). The drying process is known to induce the formation of various volatile substances
that contribute to the mushroom's aroma. Chemical analysis has shown that the odour of the dried mushroom is a complex mixture of 53 volatile compounds.
A 1998 estimate suggests the total annual worldwide consumption of Boletus edulis and closely related species (B. aereus, B. pinophilus, and B. reticulatus) to be between 20,000 and 100,000 tons. Approximately 2,700 tonnes (3,000 tons
) were sold in France, Italy and Germany in 1988, according to official figures. The true amount consumed far exceeds this, as it does not account for informal sales or consumption by collectors. They are widely exported and sold in dried form, reaching countries where they do not occur naturally, such as Australia and New Zealand. The autonomous community of Castile and León
in Spain produces 7,700 tonnes (8,500 tons) annually. In autumn, the price of porcini in the Northern Hemisphere typically ranges between $20 and $80 dollars per kilogram, although in New York in 1997, the scarcity of fruit bodies elevated the wholesale price to over $200 per kilogram.
In the vicinity of Borgotaro
in the Province of Parma
of northern Italy, the four species Boletus edulis, B. aereus, B. aestivalis and B. pinophilus have been recognised for their superior taste and officially termed Fungo di Borgotaro. Here, these mushrooms have been collected for centuries, and exported commercially. However, due to recent trends in the globalization of mushroom trade, most of the porcini commercially available in Italy or exported by Italy no longer originate from Italy. Porcini and other mushrooms are imported into Italy from various locations, especially China and eastern European countries; these are then often re-exported under the "Italian porcini" label.
In Italy, the disconnect with local production has had an adverse effect on quality; for example, in the 1990s, some of the dried porcino mushrooms exported to Italy from China contained species of genus Tylopilus
, which are rather similar in appearance, and when dried, are difficult for both mushroom labourers and mycologists alike to distinguish from Boletus. Tylopilus species typically have a very bitter taste, a bitterness that is imparted to the flavour of the porcini with which they are mixed.
After the fall of the Iron Curtain
and the economic and political barriers that followed, central and eastern European countries with local mushroom harvesting traditions, such as Albania, Bulgaria, Macedonia, Romania, Serbia and Slovenia, developed into exporters of porcini, concentrating primarily on the Italian market. Exported porcini and other wild fungi are also destined for France, Germany and other western European markets, where demand for them exists, but collection on a commercial scale does not. Picking B. edulis has become an annual seasonal income earner and pastime in countries like Bulgaria
, especially for many Roma communities and the unemployed
. Unfortunately, a lack of control has led to heavy exploitation of the mushroom resource.
As with other strictly mycorrhizal fungi, B. edulis has eluded attempts to cultivate it. The results of some studies suggest that unknown components of the soil microflora might be required for B. edulis to successfully establish a mycorrhizal relationship with the host plant.
s or fat, contains vitamin
s, minerals
and dietary fibre. Fresh mushrooms contain over 80% moisture, although reported values tend to differ somewhat as moisture content can be affected by environmental temperature and relative humidity
during growth and storage, as well as the relative amount of water that may be produced as a result of normal metabolic processes during storage.
Carbohydrates make up the bulk of the fruit bodies, comprising 9.23% of the fresh weight (see table), and 65.4% of the dry weight. The carbohydrate component contains the monosaccharide
s glucose
, mannitol
and α,α-trehalose
, the polysaccharide
glycogen
, and the water-insoluble structural polysaccharide chitin
, which accounts for up to 80–90% of dry matter in mushroom cell wall
s. Chitin, hemicellulose
, and pectin
-like carbohydrates—all indigestible by humans—contribute to the nutritionally desirable high proportion of insoluble fibre in B. edulis.
The total lipid
, or crude fat, content makes up 2.6% of the dry matter of the mushroom. The proportion of fatty acid
s (expressed as a % of total fatty acids) are: palmitic acid
, 9.8%; stearic acid
, 2.7%; oleic acid
, 36.1%; linoleic acid
, 42.2%, and linolenic acid
, 0.2%.A comparable Indian analysis produced somewhat different values: total lipids, 3.3% of dry matter; palmitic acid, 21.6%; stearic acid, 9.1%; oleic acid, 31.1%; linoleic acid, 33.8%, and linolenic acid, 1.7%. Source: Kavishree S, Hemavathy J, Lokesh BR, Shashirekha MN, Rajarathnam S. (2008). "Fat and fatty acids in Indian edible mushrooms". Food Chemistry 106: 597–602.
A comparative study of the amino acid
composition of eleven Portuguese wild edible mushroom species showed Boletus edulis to have the highest total amino acid content,Other species tested were Suillus bellinii
, Suillus luteus
, Suillus granulatus
, Tricholomopsis rutilans
, Hygrophorus agathosmus
, Amanita rubescens, Russula cyanoxantha
, Tricholoma equestre
, Fistulina hepatica, and Cantharellus cibarius. about 2.3 g per 100 g of dried mushroom. This total includes a full complement of 20 essential
and nonessential amino acids. Analysis of the free amino acids (that is, those not bound up in protein
) revealed glutamine
and alanine
to be the principal amino acids (each about 25% of total compounds); a separate analysis concluded that lysine
is another predominant compound.
Reported values of the composition and concentrations of trace metal
s and minerals in Boletus edulis tend to differ considerably, as the mushroom bioaccumulates different elements to varying degrees, and the element concentration in the fruit bodies is often a reflection of the element concentration of the soils from which they were picked. In general, B. edulis contains appreciable amounts of selenium
(13-17 ppm), a trace mineral essential for good health; however, the bioavailability
of mushroom-derived selenium is low. Whole fruit bodies also contain about 200 μg
of vitamin D2 per 100 g dry weight. The relatively high ergosterol
content (see next section) of the fruit bodies can make the mushroom nutritionally pragmatic for vegetarians and vegans, who would otherwise have a limited intake of vitamin D.
compound common in fungi. Additionally, the fruit bodies have about 30 mg of ergosterol peroxide
per 100 g of dried mushroom. Ergosterol peroxide is a steroid
derivative
with a wide spectrum of biological activity
, including antimicrobial
and anti-inflammatory
activity, and cytotoxicity
to various tumor cell lines grown in laboratory culture
.
The mushroom also contains a sugar-binding protein
, or lectin
, that has affinity for the sugars xylose
and melibiose
. The lectin is mitogenic—that is, it can stimulate cells to begin the process of cell division
, resulting in mitosis
. Further, the lectin has antiviral
properties: it inhibits the human immunodeficiency virus enzyme reverse transcriptase
. Other studies suggest that B. edulis also has antiviral activity against Vaccinia
virus and tobacco mosaic virus
grown in culture. Antiviral compounds from mushrooms are a subject of interest in biomedical research for their potential to advance the knowledge of viral replication
, and as new drugs in the treatment of viral disease.
The fruit bodies have a high antioxidative
capacity, due probably to a combination of various organic acid
s (such as oxalic
, citric
, malic
, succinic
and fumaric acid
s), phenolic compounds
and alkaloid
s; the highest antioxidant activity is in the mushroom caps. Furthermore, fruit bodies were determined to have 528 mg of the antioxidant compound ergothioneine
per kilogram of fresh mushroom; this value was the highest among many food items tested in one study. Porcini were thought to have anti-cancer properties according to Hungarian research conducted in the 1950s, but later investigations in the United States did not support this.
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
known as penny bun, porcino or cep, is a basidiomycete fungus, and the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of the genus Boletus
Boletus
Boletus is a genus of mushroom, comprising over 100 species. The genus Boletus was originally broadly defined and described by Elias Magnus Fries in 1821, essentially containing all fungi with pores...
. Widely distributed in the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
across Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
, and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, it does not occur naturally in the Southern Hemisphere, although it has been introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
to southern Africa
Southern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. Several closely related European mushrooms formerly thought to be varieties or forms
Form (botany)
In botanical nomenclature, a form is one of the "secondary" taxonomic ranks, below that of variety, which in turn is below that of species; it is an infraspecific taxon...
of B. edulis have been shown using molecular phylogenetic analysis to be distinct species, and others previously classed as separate species are conspecific with this species. The western North American species commonly known as the California king bolete (Boletus edulis var. grandedulis) is a large, darker-coloured variant that was first formally identified in 2007.
The fungus grows in deciduous and coniferous forests and tree plantations, forming symbiotic ectomycorrhizal
Mycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
associations with living trees by enveloping the tree's underground roots with sheaths of fungal tissue. The fungus produces spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
-bearing fruit bodies above ground in summer and autumn. The fruit body has a large brown cap
Pileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
which on occasion can reach 35 cm (14 in) in diameter and 3 kg (6.6 lb) in weight. Like other bolete
Bolete
A bolete is a type of fungal fruiting body characterized by the presence of a pileus that is clearly differentiated from the stipe, with a spongy surface of pores on the underside of the pileus...
s, it has tubes extending downward from the underside of the cap, rather than gills; spores escape at maturity through the tube openings, or pores. The pore surface of the B. edulis fruit body is whitish when young, but ages to a greenish-yellow. The stout stipe
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
, or stem, is white or yellowish in colour, up to 25 cm (10 in) tall and 10 cm (3.9 in) thick, and partially covered with a raised network pattern, or reticulations.
Prized as an ingredient in various foods, B. edulis is an edible mushroom
Edible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...
held in high regard in many cuisines, and is commonly prepared and eaten in soups, pasta
Pasta
Pasta is a staple food of traditional Italian cuisine, now of worldwide renown. It takes the form of unleavened dough, made in Italy, mostly of durum wheat , water and sometimes eggs. Pasta comes in a variety of different shapes that serve for both decoration and to act as a carrier for the...
, or risotto
Risotto
Risotto is a class of Italian dishes of rice cooked in broth to a creamy consistency. The broth may be meat-, fish-, or vegetable-based; many kinds include Parmesan cheese, butter, and onion...
. The mushroom is low in fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
and digestible carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s, and high in protein, vitamin
Vitamin
A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
s, mineral
Dietary mineral
Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. Examples of mineral elements include calcium, magnesium, potassium, sodium, zinc, and iodine...
s and dietary fibre. Although it is sold commercially, it has not been successfully grown in cultivation. Available fresh in autumn in Central
Central Europe
Central Europe or alternatively Middle Europe is a region of the European continent lying between the variously defined areas of Eastern and Western Europe...
, Southern
Southern Europe
The term Southern Europe, at its most general definition, is used to mean "all countries in the south of Europe". However, the concept, at different times, has had different meanings, providing additional political, linguistic and cultural context to the definition in addition to the typical...
and Northern Europe
Northern Europe
Northern Europe is the northern part or region of Europe. Northern Europe typically refers to the seven countries in the northern part of the European subcontinent which includes Denmark, Estonia, Latvia, Lithuania, Norway, Finland and Sweden...
, it is most often dried, packaged and distributed worldwide. Keeping its flavour after drying, it is then reconstituted and used in cooking. Boletus edulis is one of the few fungi that are sold pickled. The fungus also produces a variety of organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
s with a diverse spectrum of biological activity
Biological activity
In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or pharmacophore but can be modified by the other...
, including the steroid derivative ergosterol
Ergosterol
Ergosterol is a sterol found in fungi, and named for ergot, a common name for the members of the fungal genus Claviceps from which ergosterol was first isolated. Ergosterol does not occur in plant or animal cells...
, a sugar binding protein
Lectin
Lectins are sugar-binding proteins that are highly specific for their sugar moieties. They play a role in biological recognition phenomena involving cells and proteins. For example, some viruses use lectins to attach themselves to the cells of the host organism during infection...
, antiviral
Antiviral drug
Antiviral drugs are a class of medication used specifically for treating viral infections. Like antibiotics for bacteria, specific antivirals are used for specific viruses...
compounds, antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
s, and phytochelatin
Phytochelatin
Phytochelatins are oligomers of glutathione, produced by the enzyme phytochelatin synthase. They are found in plants, fungi, nematodes and all groups of algae including cyanobacteria. Phytochelatins act as chelators, and are important for heavy metal detoxification...
s, which give the organism resistance to toxic heavy metals.
Taxonomy
Species description
A species description or type description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species which have been described previously, or are...
in 1782 by the French botanist Pierre Bulliard
Jean Baptiste François Pierre Bulliard
Jean Baptiste François Pierre Bulliard was a French physician and botanist....
and still bears its original name. The starting date of fungal taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
had been set as January 1, 1821, to coincide with the date of the works of the 'father of mycology', Swedish naturalist Elias Magnus Fries
Elias Magnus Fries
-External links:*, Authors of fungal names, Mushroom, the Journal of Wild Mushrooming.*...
, which meant that the name required sanction by Fries (indicated in the name by a colon) to be considered valid, as Bulliard's work preceded this date. It was thus written Boletus edulis Bull.:Fr. However, a 1987 revision of the International Code of Botanical Nomenclature set the starting date at May 1, 1753, the date of publication of Linnaeus' seminal work, the Species Plantarum
Species Plantarum
Species Plantarum was first published in 1753, as a two-volume work by Carl Linnaeus. Its prime importance is perhaps that it is the primary starting point of plant nomenclature as it exists today. This means that the first names to be considered validly published in botany are those that appear...
. Hence the name no longer requires the ratification of Fries' authority. Early alternate names
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
include Boletus solidus by English naturalist James Sowerby
James Sowerby
James Sowerby was an English naturalist and illustrator. Contributions to published works, such as A Specimen of the Botany of New Holland or English Botany, include his detailed and appealing plates...
in 1809, and Gray's
Samuel Frederick Gray
Samuel Frederick Gray was a British botanist, mycologist, and pharmacologist. He was the father of the zoologists John Edward Gray and George Robert Gray.-Background:...
Leccinum edule. Gray's transfer of the species to Leccinum was later determined to be inconsistent with the rules of botanical nomenclature
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....
, and it is apparent that he was unfamiliar with the earlier works of Fries when he published his arrangement of bolete species.
Boletus edulis is the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of the genus Boletus
Boletus
Boletus is a genus of mushroom, comprising over 100 species. The genus Boletus was originally broadly defined and described by Elias Magnus Fries in 1821, essentially containing all fungi with pores...
. In Rolf Singer
Rolf Singer
Rolf Singer was a German-born mycologist and one of the most important taxonomists of gilled mushrooms in the 20th century....
's classification
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....
of the Agaricales
Agaricales
The fungal order Agaricales, also known as gilled mushrooms , or euagarics, contains some of the most familiar types of mushrooms. The order has 33 extant families, 413 genera, and over 13000 described species, along with five extinct genera known only from the fossil record...
mushrooms, it is also the type species of section Boletus, a grouping of about 30 related boletes united by a number of characteristics: a mild-tasting white flesh
Trama (mycology)
In mycology trama is a term for the inner, fleshy portion of a mushroom's basidiocarp, or fruit body. It is distinct from the outer layer of tissue, known as the pileipellis or cuticle, and from the spore-bearing tissue layer known as the hymenium....
that does not change colour when exposed to air; a smooth to distinctly raised netted pattern over at least the uppermost portion of the stem; a yellow-brown or olive-brown spore print
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...
; white tubes that later become yellowish then greenish, and that initially appear to be stuffed with cotton; and cystidia that are not strongly coloured. Molecular analysis published in 2006 established that the bolete mushrooms are all derived from a common ancestor
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
, and established the Boletales
Boletales
The Boletales are an order of Agaricomycetes, containing over 1300 species with a diverse array of fruiting body types. The boletes are the best known members of this group, and until recently, the Boletales were thought to only contain boletes...
as an order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
separate from the Agaricales.
The first named species of the genus Boletus
Boletus
Boletus is a genus of mushroom, comprising over 100 species. The genus Boletus was originally broadly defined and described by Elias Magnus Fries in 1821, essentially containing all fungi with pores...
, the generic
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
name is derived from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
term bōlētus "mushroom", which was borrowed in turn from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
βωλίτης, "terrestrial fungus". Ultimately, this last word derives from bōlos/βῶλος "lump", "clod", and, metaphorically, "mushroom". However, the βωλίτης of Galen
Galen
Aelius Galenus or Claudius Galenus , better known as Galen of Pergamon , was a prominent Roman physician, surgeon and philosopher...
, like the boletus of Latin writers like Martial
Martial
Marcus Valerius Martialis , was a Latin poet from Hispania best known for his twelve books of Epigrams, published in Rome between AD 86 and 103, during the reigns of the emperors Domitian, Nerva and Trajan...
, Seneca
Seneca the Younger
Lucius Annaeus Seneca was a Roman Stoic philosopher, statesman, dramatist, and in one work humorist, of the Silver Age of Latin literature. He was tutor and later advisor to emperor Nero...
and Petronius
Petronius
Gaius Petronius Arbiter was a Roman courtier during the reign of Nero. He is generally believed to be the author of the Satyricon, a satirical novel believed to have been written during the Neronian age.-Life:...
, is often identified as the much prized Amanita caesarea
Amanita caesarea
Amanita caesarea, commonly known in English as Caesar's Mushroom, is a highly regarded edible mushroom in the genus Amanita, native to southern Europe and North Africa. It has a distinctive orange cap, yellow gills and stem. Similar orange-capped species occur in North America and India...
. The specific epithet edulis in Latin means "eatable" or "edible".
Common names
Common nameCommon name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s for Boletus edulis vary by region. The standard Italian name porcino means "piglet" in Italian
Italian language
Italian is a Romance language spoken mainly in Europe: Italy, Switzerland, San Marino, Vatican City, by minorities in Malta, Monaco, Croatia, Slovenia, France, Libya, Eritrea, and Somalia, and by immigrant communities in the Americas and Australia...
, and echoes the term suilli, literally 'hog mushrooms', used by the Ancient Romans, and still surviving in Southern Italian words for this mushroom. The derivation has been ascribed to the resemblance of young fruit bodies to piglets, or to the fondness pigs have for eating them. It is also known as king bolete. The English penny bun
Penny bun
A penny bun or a penny loaf was a small bread bun or loaf which cost one old penny at the time when there were 240 pence to the pound. A penny loaf was a common size loaf of bread in England regulated by the Assize of Bread Act of 1266. However, the cost of the loaf could vary depending on the...
refers to its rounded brownish shape. The German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
name Steinpilz "stone mushroom" is derived from the firm flesh. In Austria it is called Herrenpilz, the "gentlemen's mushroom", while in Mexico, the Spanish
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...
name is panza, meaning "belly". Another Spanish name, rodellon, means "small round boulder", while the Dutch
Dutch language
Dutch is a West Germanic language and the native language of the majority of the population of the Netherlands, Belgium, and Suriname, the three member states of the Dutch Language Union. Most speakers live in the European Union, where it is a first language for about 23 million and a second...
name eekhoorntjesbrood means "squirrel's bread". In Albanian
Albanian language
Albanian is an Indo-European language spoken by approximately 7.6 million people, primarily in Albania and Kosovo but also in other areas of the Balkans in which there is an Albanian population, including western Macedonia, southern Montenegro, southern Serbia and northwestern Greece...
it is called pankushe or barkushe, the first name probably deriving from Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
and the second one its analog in Albanian meaning "the belly one" from bark=belly. In Russia and some ex-Soviet republics
Commonwealth of Independent States
The Commonwealth of Independent States is a regional organization whose participating countries are former Soviet Republics, formed during the breakup of the Soviet Union....
Boletus edulis is known as white mushroom (where "white" means "noble" as opposed to "black" i.e. common mushrooms). Its Polish
Polish language
Polish is a language of the Lechitic subgroup of West Slavic languages, used throughout Poland and by Polish minorities in other countries...
name prawdziwek stems from 'prawda' or truth, suggesting that it is the "true mushroom", reflecting its status as the king of field mushrooms in that country. In Montenegro, Bosnia and Herzegovina, Croatia and Serbia it is known as pravi vrganj (true vrganj), or more often only as vrganj, which is actually the common name for the whole Boletus genus.
The vernacular name cep is derived from the Catalan
Catalan language
Catalan is a Romance language, the national and only official language of Andorra and a co-official language in the Spanish autonomous communities of Catalonia, the Balearic Islands and Valencian Community, where it is known as Valencian , as well as in the city of Alghero, on the Italian island...
cep or its French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
name cèpe, although the latter is a generic term applying to several species. In France, it is more fully cèpe de Bordeaux, derived from the Gascon
Gascon language
Gascon is usually considered as a dialect of Occitan, even though some specialists regularly consider it a separate language. Gascon is mostly spoken in Gascony and Béarn in southwestern France and in the Aran Valley of Spain...
cep "trunk" for its fat stalk, ultimately from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
cippus "stake". Ceppatello, ceppatello buono, ceppatello bianco, giallo leonato, ghezzo, and moreccio are names from Italian dialects, and ciurenys or surenys is another term in Catalan. The French-born King Charles XIV John
Charles XIV John of Sweden
Charles XIV & III John, also Carl John, Swedish and Norwegian: Karl Johan was King of Sweden and King of Norway from 1818 until his death...
popularised B. edulis in Sweden after 1818, and is honoured in the local vernacular name Karljohanssvamp. The monarch cultivated the fungus about his residence, Rosersberg Palace
Rosersberg Palace
Rosersberg Palace is one of the Royal Palaces of Sweden. Situated on the shores of Lake Mälaren, on the outskirts of Stockholm, it was built in the 1630s by the Oxenstierna family and became a royal palace in 1762, when the state gave it to Duke Karl , the younger brother of Gustav III of Sweden.-...
. It is known as hed tab tao in Thai
Thai language
Thai , also known as Central Thai and Siamese, is the national and official language of Thailand and the native language of the Thai people, Thailand's dominant ethnic group. Thai is a member of the Tai group of the Tai–Kadai language family. Historical linguists have been unable to definitively...
.
Description
The capPileus (mycology)
The pileus is the technical name for the cap, or cap-like part, of a basidiocarp or ascocarp that supports a spore-bearing surface, the hymenium. The hymenium may consist of lamellae, tubes, or teeth, on the underside of the pileus...
of this mushroom is 7–30 cm (3–12 in) broad at maturity. Slightly sticky to touch, it is convex in shape when young and flattens with age. The colour is generally reddish-brown fading to white in areas near the margin, and continues to darken as it matures. The stipe
Stipe (mycology)
thumb|150px|right|Diagram of a [[basidiomycete]] stipe with an [[annulus |annulus]] and [[volva |volva]]In mycology a stipe refers to the stem or stalk-like feature supporting the cap of a mushroom. Like all tissues of the mushroom other than the hymenium, the stipe is composed of sterile hyphal...
, or stem, is 8–25 cm (3.5–10 in) in height, and up to 7 cm (2.8 in) thick—rather large in comparison to the cap; it is club-shaped, or bulges out in the middle. It is finely reticulate on the upper portion, but smooth or irregularly ridged on the lower part. The under surface of the cap is made of thin tubes, the site of spore
Spore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
production; they are 1 to 2 cm (0.393700787401575 to 0.78740157480315 in) deep, and whitish in colour when young, but mature to a greenish-yellow. The angular pores, which do not stain when bruised, are small — roughly 2 to 3 pores per millimetre. In youth the pores are white and appear as if stuffed with cotton (which is actually mycelia
Mycelium
thumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other...
); as they age, they change colour to yellow and later to brown. The spore print
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...
is olive brown. The flesh
Trama (mycology)
In mycology trama is a term for the inner, fleshy portion of a mushroom's basidiocarp, or fruit body. It is distinct from the outer layer of tissue, known as the pileipellis or cuticle, and from the spore-bearing tissue layer known as the hymenium....
of the fruit body is white, thick and firm when young, but becomes somewhat spongy with age. When bruised or cut, it either does not change colour, or turns a very light brown. Fully mature specimens can weigh about 1 kg (2.2 lb); a huge specimen collected on the Isle of Skye, Scotland, in 1995 bore a cap of 42 cm (16.5 in), with a stipe 18 cm (7.1 in) in height and 14 cm (5.5 in) wide, and weighed 3.2 kg (7.1 lb).
Boletus edulis is considered one of the safest wild mushrooms to pick for the table, as there are no poisonous species that closely resemble it. The most similar mushroom may be the devil's bolete (Boletus satanas), which has a similar shape, but has a red stem and stains blue on bruising. However, it is often confused with the very bitter and unpalatable Tylopilus felleus
Tylopilus felleus
Tylopilus felleus, formerly Boletus felleus, is a fungus of the bolete family, found in Northern Europe and North America. Although it is not poisonous, it is not considered edible, due to its overwhelming bitterness.-Taxonomy:...
, but can be distinguished by the reticulation on the stalk; in porcini, it is a whitish net-like pattern on a brownish stalk, whereas it is a dark pattern on white in the latter. Porcini have whitish pores while the other has pink. If in doubt, tasting a tiny bit of flesh will yield a bitter taste. It can also resemble the "bolete-like" Gyroporus castaneus
Gyroporus castaneus
Gyroporus castaneus, or commonly the chestnut bolete, is a small, white-pored relation of the Boletus mushrooms. It has a brown cap, and is usually found with oak trees. It differs from the true boletes in that the spores are a pale straw colour....
, which is generally smaller, and has a browner stem.
The spores
Basidiospore
A basidiospore is a reproductive spore produced by Basidiomycete fungi. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are produced by specialized fungal cells called basidia. In grills under a cap of one common species in the phylum of...
are elliptical to spindle-shaped, with dimensions of 12–17 by 5–7 µm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
. The basidia, the spore-bearing cells, are produced in a layer lining the tubes, and arrange themselves so their ends are facing the center of the tube; this layer of cells is known technically as a hymenium
Hymenium
The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidia or asci, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some cells develop into sterile cells called cystidia or...
. The basidia are thin-walled, mostly attached to 4 spores, and measure 25–30 by 8–10 µm. Another cell type present in the hymenium are the cystidia, larger sterile cells that protrude beyond the basidia into the lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
of the hymenium, and act as air traps, regulating humidity. B. edulis has pleurocystidia (cystidia located on the face of a pore) that are thin-walled, roughly spindle-shaped to ventricose
Ventricose
In mycology, Ventricose is a condition in which the cystidia, lamella or stipe of a mushroom is swollen in the middle....
, and measure 30–45 by 7–10 µm; the hymenium does not have cheilocystidia — cells found on the edges of the pores. The hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e of B. edulis do not have clamp connection
Clamp connection
A clamp connection is a structure formed by growing hyphal cells of certain fungi. It is created to ensure each septum, or segment of hypha separated by crossed walls, receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types...
s.
Related species
Several similar brownish-coloured species are sometimes considered subspecies or forms of this mushroom. In Europe, in addition to B. edulis (or cèpe de Bordeaux), the most popular are:- Tête de nègre ("negro’s head"; Boletus aereusBoletus aereusBoletus aereus is a bolete, an edible mushroom frequently consumed in the Basque Country, Navarre, France and Italy. It is commonly known as ontto beltza in Basque, porcino nero in Italian, and tête de nègre in French...
), much rarer than B. edulis, is more highly regarded by gourmets, and more expensive. Usually smaller than B. edulis, it is also distinctively darker in colour. It is especially suited to drying. - Cèpe des pins ("pine tree cep"; Boletus pinophilusBoletus pinophilusBoletus pinophilus, commonly known as the pine bolete or pinewood king bolete, is a basidiomycete fungus of the genus Boletus found throughout Europe. The large, edible fruiting bodies known as mushrooms appear under pine trees, generally in summer and autumn...
or Boletus pinicola) grows among pine trees. Rarer than B. edulis, it is less appreciated by gourmets than the two other kinds of porcini, but remains a mushroom rated above most others. - Cèpe d'été ("summer cep"; Boletus reticulatusBoletus reticulatusBoletus reticulatus , and commonly referred to as the summer cep is a basidiomycete fungus of the genus Boletus. It occurs in deciduous forests of Europe where it forms a symbiotic mycorrhizal relationship with species of oak...
), also less common and found earlier.
Molecular phylogenetic analyses have proven that these three are all distinctive and separate species; other taxa formerly believed to be unique species or subspecies, such as B. betulicola, B. chippewaensis, B. persoonii, B. quercicola and B. venturii, are now known to be part of a B. edulis species complex
Species complex
A species complex is a group of closely related species, where the exact demarcation between species is often unclear or cryptic owing to their recent and usually still incomplete reproductive isolation. Ring species, superspecies and cryptic species complex are example of species complex...
with a wide morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
, ecological and geographic range, and that the genetic variability in this complex is low. Similar molecular technology has been developed to rapidly and accurately identify B. edulis and other commercially important fungi.
Western North America has a number of species closely related to B. edulis. The white king bolete (Boletus barrowsii
Boletus barrowsii
Boletus barrowsii, also known in English as the white king bolete after its pale colored cap, is an edible and highly regarded fungus in the genus Boletus that inhabits southwestern North America...
), found in parts of Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, and California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
(and possibly elsewhere), is named after its discoverer Chuck Barrows. It is lighter in colour than B. edulis, having a cream-coloured cap with pink tones; often mycorrhizal with Ponderosa pine
Ponderosa Pine
Pinus ponderosa, commonly known as the Ponderosa Pine, Bull Pine, Blackjack Pine, or Western Yellow Pine, is a widespread and variable pine native to western North America. It was first described by David Douglas in 1826, from eastern Washington near present-day Spokane...
, it tends to grow in areas where there is less rainfall. Some find its flavour as good as if not better than B. edulis. The California king bolete (Boletus edulis var. grandedulis) can reach massive proportions, and is distinguished from B. edulis by a mature pore surface that is brown to slightly reddish. The cap colour appears to be affected by the amount of light received during its development, and may range from white in young specimens grown under thick canopy, to dark-brown, red-brown or yellow brown in those specimens receiving more light. The queen bolete (Boletus regineus
Boletus regineus
Boletus regineus, commonly known as the queen bolete, is an edible and highly regarded fungus of the Boletus family that inhabits southwestern North America. It was considered a variant of the similarly edible B. edulis for many years until declared a unique species in 2008. Phylogenetic analysis...
), formerly considered a variety of B. aereus, is also a choice edible. It is generally smaller than B. edulis, and unlike that species, is typically found in mixed forests. The spring king bolete (Boletus rex-veris
Boletus rex-veris
Boletus rex-veris, commonly known as the spring king bolete, is a basidiomycete fungus of the genus Boletus found in western North America. The large, edible fruiting bodies known as mushrooms appear under pine trees, generally in May to June. It has a pinkish to brownish cap and its stem is often...
), formerly considered a variety of B. edulis or B. pinophilus, is found throughout western North America. In contrast to B. edulis, B. rex-veris tends to fruit in clusters, and, as its common name suggests, appears in the spring.
Habitat and distribution
The fruit bodies of Boletus edulis can grow singly or in small clusters of two or three specimens. The mushroom's habitat consists of areas dominated by pine (Pinus spp.), spruce (Picea spp.), hemlock (TsugaTsuga
Tsuga is a genus of conifers in the family Pinaceae. The common name hemlock is derived from a perceived similarity in the smell of its crushed foliage to that of the unrelated plant poison hemlock....
spp.) and fir (Abies spp.) trees, although other hosts include chestnut
Chestnut
Chestnut , some species called chinkapin or chinquapin, is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae, native to temperate regions of the Northern Hemisphere. The name also refers to the edible nuts they produce.-Species:The chestnut belongs to the...
, chinquapin
Chrysolepis
Chrysolepis is a small genus in the beech family Fagaceae, endemic to the western United States. Its two species have the common name chinquapin...
, beech
Beech
Beech is a genus of ten species of deciduous trees in the family Fagaceae, native to temperate Europe, Asia and North America.-Habit:...
, Keteleeria
Keteleeria
Keteleeria is a genus of three species of coniferous trees in the family Pinaceae, related to the genera Nothotsuga and Pseudolarix. It is distinguished from Nothotsuga by the much larger cones, and from Pseudolarix by the evergreen leaves and the cones not disintegrating readily at maturity...
spp., Lithocarpus
Lithocarpus
Lithocarpus is a genus in the beech family Fagaceae, differing from Quercus in the erect male spikes. The World Checklist accepts 334 species, though some other texts suggest as few as 100 species. About 100 Asian species of the genus were formerly treated in the genus Pasania. All but one are...
spp., and oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
. In California, porcini have been collected in a variety of forests, such as coastal forests, dry interior oak forests and savanna
Savanna
A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...
s and interior high-elevation montane
Montane
In biogeography, montane is the highland area located below the subalpine zone. Montane regions generally have cooler temperatures and often have higher rainfall than the adjacent lowland regions, and are frequently home to distinct communities of plants and animals.The term "montane" means "of the...
mixed forests, to an altitude of 3,500 m (11,500 ft). In northwestern Spain, they are common in scrublands dominated by the rock rose
Cistaceae
The Cistaceae is a small family of plants known for its beautiful shrubs, which are profusely covered by flowers at the time of blossom...
species Cistus ladanifer and Halimium lasianthum.
Boletus edulis has a cosmopolitan distribution
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
, concentrated in cool-temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
to subtropical regions. It is common in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
—from northern Scandinavia, south to the extremities of Greece and Italy—and North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, where its southern range extends as far south as Mexico. It is well known from the Borgotaro area of Parma
Parma
Parma is a city in the Italian region of Emilia-Romagna famous for its ham, its cheese, its architecture and the fine countryside around it. This is the home of the University of Parma, one of the oldest universities in the world....
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, and has PGI
Protected designation of origin
Protected Geographical Status is a legal framework defined in European Union law to protect the names of regional foods. Protected Designation of Origin , Protected Geographical Indication and Traditional Speciality Guaranteed are distinct regimes of geographical indications within the framework...
status there. The European distribution extends north to Scandinavia and south to southern Italy and Morocco. In China, the mushroom can be found from the northeastern Heilongjiang Province to the Yunnan-Guizhou Plateau and Tibet
Tibet
Tibet is a plateau region in Asia, north-east of the Himalayas. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpas, Qiang, and Lhobas, and is now also inhabited by considerable numbers of Han and Hui people...
. It has been recorded growing under Pinus and Tsuga in Sagarmatha National Park
Sagarmatha National Park
Sagarmāthā National Park is a protected area in the Himalayas of eastern Nepal containing the southern half of Mount Everest. The park was created on July 19, 1976 and was inscribed as a Natural World Heritage Site in 1979...
in Nepal
Nepal
Nepal , officially the Federal Democratic Republic of Nepal, is a landlocked sovereign state located in South Asia. It is located in the Himalayas and bordered to the north by the People's Republic of China, and to the south, east, and west by the Republic of India...
, as well as in the India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
n forests of Arunachal Pradesh
Arunachal Pradesh
Arunachal Pradesh is a state of India, located in the far northeast. It borders the states of Assam and Nagaland to the south, and shares international borders with Burma in the east, Bhutan in the west, and the People's Republic of China in the north. The majority of the territory is claimed by...
.
Non-native introductions
Boletus edulis grows in some areas where it is not believed to be indigenousIndigenous (ecology)
In biogeography, a species is defined as native to a given region or ecosystem if its presence in that region is the result of only natural processes, with no human intervention. Every natural organism has its own natural range of distribution in which it is regarded as native...
. It is often found underneath oak and silver birch in Hagley Park
Hagley Park
Hagley Park is the largest urban open space in Christchurch, New Zealand, and was created in 1855 by the Provincial Government. According to the government's decree at that time, Hagley Park is "reserved forever as a public park, and shall be open for the recreation and enjoyment of the public."...
in central Christchurch
Christchurch
Christchurch is the largest city in the South Island of New Zealand, and the country's second-largest urban area after Auckland. It lies one third of the way down the South Island's east coast, just north of Banks Peninsula which itself, since 2006, lies within the formal limits of...
, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, where it is likely to have been introduced
Introduced species
An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...
, probably on the roots of container-grown beech, birch, and oak in the mid-19th century—around the time exotic trees began to be planted in the Christchurch area. It has been growing plentifully in association with pine forests in the southern KwaZulu-Natal Midlands
KwaZulu-Natal Midlands
The KwaZulu-Natal Midlands is an inland area of KwaZulu-Natal, South Africa that lies outside of Pietermaritzburg but before the Drakensberg mountain range....
in South Africa for more than 50 years and is believed to have been introduced with the import of pine trees. It also grows in pine plantations in neighboring Zimbabwe.
Ecology
Fruit body production
Although Italian folklore holds that porcini sprout up at the time of the new moon, a number of research studies have tried to investigate more scientifically the factors that influence the production of fruit bodies. Although fruit bodies may appear any time from summer to autumn, their growth is known to be triggered by rainfall during warm periods of weather followed by frequent autumn rain with a drop in soil temperature. Above average rainfall may result in the rapid appearance of large numbers of boletes, in what is known in some circles as a "bolete year". A 2004 field study indicated that fruit body production is enhanced by an open and sunny wood habitat, corroborating an earlier observation made in a Zimbabwean study; removal of the litter layer on the forest floorForest floor
The forest floor, also called detritus, duff and the O horizon, is one of the most distinctive features of a forest ecosystem. It mainly consists of shed vegetative parts, such as leaves, branches, bark, and stems, existing in various stages of decomposition above the soil surface...
appeared to have a negative effect on fruit body production, but previous studies reported contradictory results. A Lithuanian study conducted in 2001 concluded that the maximal daily growth rate of the cap (about 21 mm or 0.8 in) occurred when the relative air humidity was the greatest, and the fruit bodies ceased growing when the air humidity dropped below 40%. Factors most likely to inhibit the appearance of fruit bodies included prolonged drought, inadequate air and soil humidity, sudden decreases of night air temperatures, and the appearance of the first frost
Frost
Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water. Frost crystals' size differ depending on time and water vapour available. Frost is also usually...
. Plots facing north tend to produce more mushrooms compared to equivalent plots facing south.
Mycorrhizal associations
Boletus edulis is mycorrhizaMycorrhiza
A mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant....
l—it is in a mutualistic relationship with the roots of plants ("hosts"), in which the fungus exchanges mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s extracted from the environment for fixed carbon
Carbon fixation
In biology, carbon fixation is the reduction of carbon dioxide to organic compounds by living organisms. The obvious example is photosynthesis. Carbon fixation requires both a source of energy such as sunlight, and an electron donor such as water. All life depends on fixed carbon. Organisms that...
from the host. Other benefits for the plant are evident: in the case of the Chinese Chestnut
Castanea mollissima
Castanea mollissima is a member of the family Fagaceae, and a species of chestnut native to China.- Description :...
, the formation of mycorrhizae with B. edulis increases the ability of plant seedlings to resist water stress
Water stress
Researchers define water stress and water scarcity in different ways. For example, some have presented maps showing the physical existence of water in nature to show nations with lower or higher volumes of water available for use. Others have related water availability to population...
, and increases leaf succulence, leaf area, and water-holding ability. The fungus forms a sheath of tissue around terminal, nutrient-absorbing rootlets of the host, forming so-called "ectomycorrhizae"; the fungal hypha
Hypha
A hypha is a long, branching filamentous structure of a fungus, and also of unrelated Actinobacteria. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium; yeasts are unicellular fungi that do not grow as hyphae.-Structure:A hypha consists of one or...
e emanate throughout the soil, effectively increasing the surface area for nutrient absorption, and the fungus penetrates between cells of the cortex
Cortex (botany)
In botany, the cortex is the outer layer of the stem or root of a plant, bounded on the outside by the epidermis and on the inside by the endodermis. It is composed mostly of undifferentiated cells, usually large thin-walled parenchyma cells of the ground tissue system. The outer cortical cells...
to facilitate nutrient exchange. Compatible hosts may belong to multiple families of vascular plant
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
s that are widely distributed throughout the Northern Hemisphere; according to one 1995 estimate, there are at least 30 host plant species distributed over more than 15 genera. Examples of mycorrhizal associates include Chinese red pine
Pinus massoniana
Pinus massoniana is a species of pine, native to a wide area of central and southern China, including Hong Kong and Taiwan, and northern Vietnam, growing at low to moderate altitudes, mostly below 1,500 m but rarely up to 2,000 m altitude.- Description :It is an evergreen tree reaching 25-45 m in...
, Mexican weeping pine
Pinus patula
Patula pine, pino patula, pinus patula is a tree native to the highlands of Mexico. It grows from 24° to 18° North latitude and 1800 to 2700 m above sea level. 30 m tall...
, Scots pine, Norway spruce, Coast Douglas-fir, mountain pine, and Virginia pine. The fungus has also been shown to associate with Gum rockrose, a pioneer
Pioneer species
Pioneer species are species which colonize previously uncolonized land, usually leading to ecological succession. They are the first organisms to start the chain of events leading to a livable biosphere or ecosystem...
early stage shrub that is adapted for growth in degraded areas, such as burned forests. These and other Rockrose
Cistus
Cistus is a genus of flowering plants in the rockrose family Cistaceae, containing about 20 species . They are perennial shrubs found on dry or rocky soils throughout the Mediterranean region, from Morocco and Portugal through to the Middle East, and also on the Canary Islands...
species are ecologically important as fungal reservoirs, maintaining an inoculum of mycorrhizal fungi for trees that appear later in the forest regrowth cycle
Ecological succession
Ecological succession, is the phenomenon or process by which a community progressively transforms itself until a stable community is formed. It is a fundamental concept in ecology, and refers to more or less predictable and orderly changes in the composition or structure of an ecological community...
.
The mushroom has been noted to commonly co-occur with Amanita muscaria
Amanita muscaria
Amanita muscaria, commonly known as the fly agaric or fly amanita , is a poisonous and psychoactive basidiomycete fungus, one of many in the genus Amanita...
or A. rubescens, although it is unclear whether this is due to a biological association between the species, or because of similarities in growing season, habitat, and ecological requirements. An association has also been reported between B. edulis and Amanita excelsa on Pinus radiata ectomycorrhizae in New Zealand, suggesting that other fungi may influence the life cycle of porcini. A 2007 field study revealed little correlation between the abundance of fruit bodies and presence of its mycelia below ground, even when soil samples were taken from directly beneath the mushroom; the study concluded "Factors triggering formation of mycorrhizae and fructification of porcini appear to be too complex to be simply explained on the basis of the amount of fungal mycelia in the soil."
Heavy metal contamination
Boletus edulis is known to be able to tolerate and even thrive on soil that is contaminated with toxic heavy metals, such as soil that might be found near metal smeltersSmelting
Smelting is a form of extractive metallurgy; its main use is to produce a metal from its ore. This includes iron extraction from iron ore, and copper extraction and other base metals from their ores...
. The mushroom's resistance to heavy metal toxicity is conferred by a biochemical called a phytochelatin
Phytochelatin
Phytochelatins are oligomers of glutathione, produced by the enzyme phytochelatin synthase. They are found in plants, fungi, nematodes and all groups of algae including cyanobacteria. Phytochelatins act as chelators, and are important for heavy metal detoxification...
—an oligopeptide
Oligopeptide
An oligopeptide consists of between 2 and 20 amino acids and includes dipeptides, tripeptides, tetrapeptides, pentapeptides, etc.Examples of oligopeptides include:...
whose production is induced after exposure to metal. Phytochelatins are chelating agents
Chelation
Chelation is the formation or presence of two or more separate coordinate bonds between apolydentate ligand and a single central atom....
, capable of forming multiple bonds with the metal; in this state, the metal cannot normally react with other elements or ions and is stored in a detoxified form in the mushroom tissue.
Pests and predators
The fruit bodies of B. edulis can be infected by the parasitic mould-like fungus Hypomyces chrysospermusHypomyces chrysospermus
The bolete eater is a parasitic ascomycete that grows on boletes, turning them a whitish, golden yellow, or tan color. It is found in Europe and North America, as well as southwest Western Australia...
, known as the bolete eater, which manifests itself as a white, yellow, or reddish-brown cottony layer over the surface of the mushroom. Some reported cases of stomach ache
Abdominal pain
Abdominal pain can be one of the symptoms associated with transient disorders or serious disease. Making a definitive diagnosis of the cause of abdominal pain can be difficult, because many diseases can result in this symptom. Abdominal pain is a common problem...
following consumption of dried porcini have been attributed to the presence of this mould on the fruit bodies. The mushroom is also used as a food source by several species of mushroom flies, as well as other insects and their larvae
Larvae
In Roman mythology, lemures were shades or spirits of the restless or malignant dead, and are probably cognate with an extended sense of larvae as disturbing or frightening...
. An unidentified species of virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
was reported to have infected specimens found in the Netherlands and in Italy; fruit bodies affected by the virus had relatively thick stems and small or no caps, leading to the name "little-cap disease".
Boletus edulis is a food source for animals such as the banana slug
Banana slug
Banana slug is a common name for three species of air-breathing land slug in the genus Ariolimax. These slugs are often yellow in color and are sometimes spotted with brown like a ripe banana....
(Ariolimax columbianus), the Long-haired Grass Mouse
Long-haired Grass Mouse
Abrothrix longipilis, also known as the Long-haired Grass Mouse or Long-haired Akodont, is a species of rodent in the family Cricetidae....
, the Red Squirrel
Red Squirrel
The red squirrel or Eurasian red squirrel is a species of tree squirrel in the genus Sciurus common throughout Eurasia...
, and, as noted in one isolated report, the Fox Sparrow
Fox Sparrow
The Fox Sparrow is a large American sparrow. It is the only member of the genus Passerella, although some authors split the genus into four species .-Taxonomy:...
.
Culinary uses
Boletus edulis, like its name implies, is an edible mushroomEdible mushroom
Edible mushrooms are the fleshy and edible fruiting bodies of several species of fungi. Mushrooms belong to the macrofungi, because their fruiting structures are large enough to be seen with the naked eye. They can appear either below ground or above ground where they may be picked by hand...
. Italian chef and restaurateur Antonio Carluccio
Antonio Carluccio
Antonio Carluccio, OBE OMRI is an Italian chef, restaurateur and food expert, based in London.-Biography:Antonio Carluccio was born in Vietri sul Mare, Salerno, Italy. His father was a stationmaster, and he moved with his father's job when he was young and grew up in Piedmont...
has described it as representing "the wild mushroom par excellence", and hails it as the most rewarding of all fungi in the kitchen for its taste and versatility. Considered a choice edible, particularly in France, Germany and Italy, it was widely written about by the Roman writers Pliny the Elder
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...
and Martial
Martial
Marcus Valerius Martialis , was a Latin poet from Hispania best known for his twelve books of Epigrams, published in Rome between AD 86 and 103, during the reigns of the emperors Domitian, Nerva and Trajan...
, although ranked below the esteemed Amanita caesarea
Amanita caesarea
Amanita caesarea, commonly known in English as Caesar's Mushroom, is a highly regarded edible mushroom in the genus Amanita, native to southern Europe and North Africa. It has a distinctive orange cap, yellow gills and stem. Similar orange-capped species occur in North America and India...
.
wrote the disgruntled Martial when served suilli instead of boleti. The term suilli was also thought to encompass the related Leccinum scabrum.
The flavour has been described as nutty and slightly meaty, with a smooth, creamy texture, and a distinctive aroma reminiscent of sourdough
Sourdough
Sourdough is a dough containing a Lactobacillus culture, usually in symbiotic combination with yeasts. It is one of two principal means of biological leavening in bread baking, along with the use of cultivated forms of yeast . It is of particular importance in baking rye-based breads, where yeast...
. Young, small porcini are most appreciated by gourmets, as the large ones often harbor maggot
Maggot
In everyday speech the word maggot means the larva of a fly ; it is applied in particular to the larvae of Brachyceran flies, such as houseflies, cheese flies, and blowflies, rather than larvae of the Nematocera, such as mosquitoes and Crane flies...
s (insect larvae), and become slimy, soft and less tasty with age. Fruit bodies are collected by holding the stipe near the base and twisting gently. Cutting the stipe with a knife may risk the part left behind rotting and the mycelium
Mycelium
thumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other...
being destroyed. Peeling and washing are not recommended. The fruit bodies are highly perishable
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...
, due largely to the high water content (around 90%), the high level of enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
activity, and the presence of a flora of microorganisms. Caution should be exercised when collecting specimens from potentially polluted or contaminated
Soil contamination
Soil contamination or soil pollution is caused by the presence of xenobiotic chemicals or other alteration in the natural soil environment....
sites, as several studies have shown that the fruit bodies can bioaccumulate
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
toxic heavy metals like mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
, cadmium
Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
, caesium
Caesium
Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C , which makes it one of only five elemental metals that are liquid at room temperature...
and polonium
Polonium
Polonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie Skłodowska-Curie and Pierre Curie. A rare and highly radioactive element, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Polonium has been studied for...
. Bioaccumulated metals or radioactive fission decay products
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
are like chemical signatures: chemical
Analytical chemistry
Analytical chemistry is the study of the separation, identification, and quantification of the chemical components of natural and artificial materials. Qualitative analysis gives an indication of the identity of the chemical species in the sample and quantitative analysis determines the amount of...
and radiochemical
Radiochemistry
Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes...
analysis can be used to identify the origin of imported specimens, and for long-term radioecological
Radioecology
Radioecology is a branch of ecology, which studies how radioactive substances interact with nature; how different mechanisms affect the substances’ migration and uptake in food chain and ecosystems...
monitoring of polluted areas.
Porcini are sold fresh in markets in summer and autumn in Central
Central Europe
Central Europe or alternatively Middle Europe is a region of the European continent lying between the variously defined areas of Eastern and Western Europe...
and Southern Europe
Southern Europe
The term Southern Europe, at its most general definition, is used to mean "all countries in the south of Europe". However, the concept, at different times, has had different meanings, providing additional political, linguistic and cultural context to the definition in addition to the typical...
, and dried or canned at other times of the year, and distributed worldwide to countries where they are not otherwise found. They are eaten and enjoyed raw, sautéed with butter, ground into pasta, in soups, and in many other dishes. In France, they are used in recipes such as cèpes à la Bordelaise, cèpe frits and cèpe aux tomates. Porcini risotto
Risotto
Risotto is a class of Italian dishes of rice cooked in broth to a creamy consistency. The broth may be meat-, fish-, or vegetable-based; many kinds include Parmesan cheese, butter, and onion...
is a traditional Italian autumn dish. Porcini are a feature of many cuisines, including Provençal
Provence
Provence ; Provençal: Provença in classical norm or Prouvènço in Mistralian norm) is a region of south eastern France on the Mediterranean adjacent to Italy. It is part of the administrative région of Provence-Alpes-Côte d'Azur...
, and Viennese
Vienna
Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...
. They are used in soups and consumed blanched in salads in Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
. Porcini can also be frozen — either raw or first cooked in butter. The colour, aroma, and taste of frozen porcini deteriorate noticeably if frozen longer than four months. Blanching or soaking and blanching as a processing step before freezing can extend the freezer life up to 12 months. They are also one of the few mushroom species pickled and sold commercially.
Dried
Soybean
The soybean or soya bean is a species of legume native to East Asia, widely grown for its edible bean which has numerous uses...
s. However, some of this content is indigestible, though digestibility is improved with cooking.
Like other boletes, porcini can be dried by being strung separately on twine and hung close to the ceiling of a kitchen. Alternatively, the mushrooms can be dried by cleaning with a brush (washing is not recommended), and then placing them in a wicker basket or bamboo steamer
Mushiki
Mushiki or seiro are two different types of Japanese steamers.Mushiki are round steamers made from bamboo like those used in Chinese cuisine. They can be stacked on top of each other so that the steam can cook many different servings simultaneously...
on top of a boiler or hot water tank. Another method is drying in an oven at 25 to 30 °C (77 to 86 F) for two to three hours, then increasing the temperature to 50 °C (122 °F) until crisp or brittle. Once dry, they are kept in an airtight jar. Importantly for commercial production, porcini retain their flavour after industrial preparation in a pressure cooker
Pressure cooking
Pressure cooking is a method of cooking in a sealed vessel that does not permit air or liquids to escape below a preset pressure. Because the boiling point of water increases as the pressure increases, the pressure built up inside the cooker allows the liquid in the pot to rise to a higher...
or after canning or bottling, and are thus useful for manufacturers of soups or stews. The addition of a few pieces of dried porcino can significantly add to flavour, and they are a major ingredient of the pasta sauce known as carrettiere (carter's sauce). The drying process is known to induce the formation of various volatile substances
Volatile organic compound
Volatile organic compounds are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and...
that contribute to the mushroom's aroma. Chemical analysis has shown that the odour of the dried mushroom is a complex mixture of 53 volatile compounds.
Commercial harvest
Short ton
The short ton is a unit of mass equal to . In the United States it is often called simply ton without distinguishing it from the metric ton or the long ton ; rather, the other two are specifically noted. There are, however, some U.S...
) were sold in France, Italy and Germany in 1988, according to official figures. The true amount consumed far exceeds this, as it does not account for informal sales or consumption by collectors. They are widely exported and sold in dried form, reaching countries where they do not occur naturally, such as Australia and New Zealand. The autonomous community of Castile and León
Castile and León
Castile and León is an autonomous community in north-western Spain. It was so constituted in 1983 and it comprises the historical regions of León and Old Castile...
in Spain produces 7,700 tonnes (8,500 tons) annually. In autumn, the price of porcini in the Northern Hemisphere typically ranges between $20 and $80 dollars per kilogram, although in New York in 1997, the scarcity of fruit bodies elevated the wholesale price to over $200 per kilogram.
In the vicinity of Borgotaro
Borgo Val di Taro
Borgo Val di Taro is a town and comune in Emilia, Italy, in the Province of Parma, 63 km from the city of Parma.Borgo Val di Taro is an important centre for cattle husbandry in Emilia and it's one of the zones where Parmigiano-Reggiano is produced....
in the Province of Parma
Province of Parma
The Province of Parma is a province in the Emilia-Romagna region of Italy. Its capital is the city of Parma.It has an area of 3,449 km², and a total population of 413,198...
of northern Italy, the four species Boletus edulis, B. aereus, B. aestivalis and B. pinophilus have been recognised for their superior taste and officially termed Fungo di Borgotaro. Here, these mushrooms have been collected for centuries, and exported commercially. However, due to recent trends in the globalization of mushroom trade, most of the porcini commercially available in Italy or exported by Italy no longer originate from Italy. Porcini and other mushrooms are imported into Italy from various locations, especially China and eastern European countries; these are then often re-exported under the "Italian porcini" label.
In Italy, the disconnect with local production has had an adverse effect on quality; for example, in the 1990s, some of the dried porcino mushrooms exported to Italy from China contained species of genus Tylopilus
Tylopilus
Tylopilus is a large genus of around 75 species of mycorrhizal bolete fungi separated from Boletus. Its best known member is the bitter bolete , the only species found in Europe. More species are found in North America, such as the edible species Tylopilus chromapes and T. alboater, and the...
, which are rather similar in appearance, and when dried, are difficult for both mushroom labourers and mycologists alike to distinguish from Boletus. Tylopilus species typically have a very bitter taste, a bitterness that is imparted to the flavour of the porcini with which they are mixed.
After the fall of the Iron Curtain
Iron Curtain
The concept of the Iron Curtain symbolized the ideological fighting and physical boundary dividing Europe into two separate areas from the end of World War II in 1945 until the end of the Cold War in 1989...
and the economic and political barriers that followed, central and eastern European countries with local mushroom harvesting traditions, such as Albania, Bulgaria, Macedonia, Romania, Serbia and Slovenia, developed into exporters of porcini, concentrating primarily on the Italian market. Exported porcini and other wild fungi are also destined for France, Germany and other western European markets, where demand for them exists, but collection on a commercial scale does not. Picking B. edulis has become an annual seasonal income earner and pastime in countries like Bulgaria
Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...
, especially for many Roma communities and the unemployed
Unemployment
Unemployment , as defined by the International Labour Organization, occurs when people are without jobs and they have actively sought work within the past four weeks...
. Unfortunately, a lack of control has led to heavy exploitation of the mushroom resource.
As with other strictly mycorrhizal fungi, B. edulis has eluded attempts to cultivate it. The results of some studies suggest that unknown components of the soil microflora might be required for B. edulis to successfully establish a mycorrhizal relationship with the host plant.
Nutritional composition
Boletus edulis constitutes a food source which, although not rich in easily absorbed carbohydrateCarbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s or fat, contains vitamin
Vitamin
A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
s, minerals
Dietary mineral
Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. Examples of mineral elements include calcium, magnesium, potassium, sodium, zinc, and iodine...
and dietary fibre. Fresh mushrooms contain over 80% moisture, although reported values tend to differ somewhat as moisture content can be affected by environmental temperature and relative humidity
Relative humidity
Relative humidity is a term used to describe the amount of water vapor in a mixture of air and water vapor. It is defined as the partial pressure of water vapor in the air-water mixture, given as a percentage of the saturated vapor pressure under those conditions...
during growth and storage, as well as the relative amount of water that may be produced as a result of normal metabolic processes during storage.
Carbohydrates make up the bulk of the fruit bodies, comprising 9.23% of the fresh weight (see table), and 65.4% of the dry weight. The carbohydrate component contains the monosaccharide
Monosaccharide
Monosaccharides are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose , fructose , galactose, xylose...
s glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
, mannitol
Mannitol
Mannitol is a white, crystalline organic compound with the formula . This polyol is used as an osmotic diuretic agent and a weak renal vasodilator...
and α,α-trehalose
Trehalose
Trehalose, also known as mycose or tremalose, is a natural alpha-linked disaccharide formed by an α,α-1,1-glucoside bond between two α-glucose units. In 1832, H.A.L. Wiggers discovered trehalose in an ergot of rye, and in 1859 Marcellin Berthelot isolated it from trehala manna, a substance made...
, the polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...
, and the water-insoluble structural polysaccharide chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
, which accounts for up to 80–90% of dry matter in mushroom cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
s. Chitin, hemicellulose
Hemicellulose
A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...
, and pectin
Pectin
Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...
-like carbohydrates—all indigestible by humans—contribute to the nutritionally desirable high proportion of insoluble fibre in B. edulis.
The total lipid
Lipid
Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...
, or crude fat, content makes up 2.6% of the dry matter of the mushroom. The proportion of fatty acid
Fatty acid
In chemistry, especially biochemistry, a fatty acid is a carboxylic acid with a long unbranched aliphatic tail , which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from...
s (expressed as a % of total fatty acids) are: palmitic acid
Palmitic acid
Palmitic acid, or hexadecanoic acid in IUPAC nomenclature, is one of the most common saturated fatty acids found in animals and plants. Its molecular formula is CH314CO2H. As its name indicates, it is a major component of the oil from palm trees . Palmitate is a term for the salts and esters of...
, 9.8%; stearic acid
Stearic acid
Stearic acid is the saturated fatty acid with an 18 carbon chain and has the IUPAC name octadecanoic acid. It is a waxy solid, and its chemical formula is CH316CO2H. Its name comes from the Greek word στέαρ "stéatos", which means tallow. The salts and esters of stearic acid are called stearates...
, 2.7%; oleic acid
Oleic acid
Oleic acid is a monounsaturated omega-9 fatty acid found in various animal and vegetable fats. It has the formula CH37CH=CH7COOH. It is an odorless, colourless oil, although commercial samples may be yellowish. The trans isomer of oleic acid is called elaidic acid...
, 36.1%; linoleic acid
Linoleic acid
Linoleic acid is an unsaturated n-6 fatty acid. It is a colorless liquid at room temperature. In physiological literature, it has a lipid number of 18:2...
, 42.2%, and linolenic acid
Alpha-linolenic acid
α-Linolenic acid is an organic compound found in many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is given the name 18:3 ....
, 0.2%.A comparable Indian analysis produced somewhat different values: total lipids, 3.3% of dry matter; palmitic acid, 21.6%; stearic acid, 9.1%; oleic acid, 31.1%; linoleic acid, 33.8%, and linolenic acid, 1.7%. Source: Kavishree S, Hemavathy J, Lokesh BR, Shashirekha MN, Rajarathnam S. (2008). "Fat and fatty acids in Indian edible mushrooms". Food Chemistry 106: 597–602.
A comparative study of the amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
composition of eleven Portuguese wild edible mushroom species showed Boletus edulis to have the highest total amino acid content,Other species tested were Suillus bellinii
Suillus bellinii
Suillus bellinii is a pored mushroom of the genus Suillus in the Suillaceae family. It is found in coastal pine forests of southern Europe.-Description:...
, Suillus luteus
Suillus luteus
Suillus luteus is a basidiomycete fungus, and the type species of the genus Suillus. It is a common fungus indigenous to coniferous forests of Eurasia and North America, and introduced to southern Australia and New Zealand...
, Suillus granulatus
Suillus granulatus
Suillus granulatus is a pored mushroom of the genus Suillus in the Suillaceae family. It is similar to the related S. luteus, but can be distinguished by its ringless stalk. Like S. luteus, it is an edible mushroom that often grows in a symbiosis with pine...
, Tricholomopsis rutilans
Tricholomopsis rutilans
Tricholomopsis rutilans, known by the unusual but apt common name of Plums and Custard or, less commonly Red-haired agaric, is a species of gilled mushroom found across Europe and North America.-Description:...
, Hygrophorus agathosmus
Hygrophorus agathosmus
Hygrophorus agathosmus, commonly known as the gray almond waxy cap or the almond woodwax, is a species of fungus in the Hygrophoraceae family. It was first described by Elias Magnus Fries in 1815; Fries gave it its current name in 1838...
, Amanita rubescens, Russula cyanoxantha
Russula cyanoxantha
Russula cyanoxantha, synonymous with R. xyanoxantha, commonly known as the charcoal burner, is a basidiomycete mushroom, distinguished from most other members of the Russula genus by the fact that its gills do not split, but are soft and flexible. It is one of the most common species of Russula in...
, Tricholoma equestre
Tricholoma equestre
Tricholoma equestre or Tricholoma flavovirens, also known as Man on horseback or Yellow knight is a formerly widely eaten but hazardous fungus of the Tricholoma genus that forms ectomycorrhiza with pine trees....
, Fistulina hepatica, and Cantharellus cibarius. about 2.3 g per 100 g of dried mushroom. This total includes a full complement of 20 essential
Essential amino acid
An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism , and therefore must be supplied in the diet.-Essentiality vs. conditional essentiality in humans:...
and nonessential amino acids. Analysis of the free amino acids (that is, those not bound up in protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
) revealed glutamine
Glutamine
Glutamine is one of the 20 amino acids encoded by the standard genetic code. It is not recognized as an essential amino acid but may become conditionally essential in certain situations, including intensive athletic training or certain gastrointestinal disorders...
and alanine
Alanine
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
to be the principal amino acids (each about 25% of total compounds); a separate analysis concluded that lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
is another predominant compound.
Reported values of the composition and concentrations of trace metal
Trace metal
Trace metals are metals in extremely small quantities that reside in or are present in animal and plant cells and tissue. They are a necessary part of good nutrition, although they can be toxic if ingested in excess quantities....
s and minerals in Boletus edulis tend to differ considerably, as the mushroom bioaccumulates different elements to varying degrees, and the element concentration in the fruit bodies is often a reflection of the element concentration of the soils from which they were picked. In general, B. edulis contains appreciable amounts of selenium
Selenium
Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...
(13-17 ppm), a trace mineral essential for good health; however, the bioavailability
Bioavailability
In pharmacology, bioavailability is a subcategory of absorption and is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered...
of mushroom-derived selenium is low. Whole fruit bodies also contain about 200 μg
Microgram
In the metric system, a microgram is a unit of mass equal to one millionth of a gram , or 1/1000 of a milligram. It is one of the smallest units of mass commonly used...
of vitamin D2 per 100 g dry weight. The relatively high ergosterol
Ergosterol
Ergosterol is a sterol found in fungi, and named for ergot, a common name for the members of the fungal genus Claviceps from which ergosterol was first isolated. Ergosterol does not occur in plant or animal cells...
content (see next section) of the fruit bodies can make the mushroom nutritionally pragmatic for vegetarians and vegans, who would otherwise have a limited intake of vitamin D.
Bioactive compounds
Boletus edulis fruit bodies contain about 500 mg of ergosterol per 100 g of dried mushroom. Ergosterol is a sterolSterol
Sterols, also known as steroid alcohols, are a subgroup of the steroids and an important class of organic molecules. They occur naturally in plants, animals, and fungi, with the most familiar type of animal sterol being cholesterol...
compound common in fungi. Additionally, the fruit bodies have about 30 mg of ergosterol peroxide
Ergosterol peroxide
Ergosterol peroxide is a steroid derivative. It has been isolated from a variety of fungi, yeast, lichens and sponges, and has been reported to exhibit immunosuppressive, anti-inflammatory, antiviral, and antitumor activities....
per 100 g of dried mushroom. Ergosterol peroxide is a steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
derivative
Derivative (chemistry)
In chemistry, a derivative is a compound that is derived from a similar compound by some chemical or physical process. In the past it was also used to mean a compound that can be imagined to arise from another compound, if one atom is replaced with another atom or group of atoms, but modern...
with a wide spectrum of biological activity
Biological activity
In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or pharmacophore but can be modified by the other...
, including antimicrobial
Antimicrobial
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...
and anti-inflammatory
Anti-inflammatory
Anti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, which affect the central nervous system....
activity, and cytotoxicity
Cytotoxicity
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are a chemical substance, an immune cell or some types of venom .-Cell physiology:...
to various tumor cell lines grown in laboratory culture
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, or lectin
Lectin
Lectins are sugar-binding proteins that are highly specific for their sugar moieties. They play a role in biological recognition phenomena involving cells and proteins. For example, some viruses use lectins to attach themselves to the cells of the host organism during infection...
, that has affinity for the sugars xylose
Xylose
Xylose is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group. It is the precursor to hemicellulose, one of the main constituents of biomass...
and melibiose
Melibiose
Melibiose is a reducing disaccharide formed by an alpha-1,6 linkage between galactose and glucose . It can be formed by invertase mediated hydrolysis of raffinose, which produces melibiose and fructose. Melibiose can be broken down into its component saccharides, glucose and galactose, by the...
. The lectin is mitogenic—that is, it can stimulate cells to begin the process of cell division
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...
, resulting in mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
. Further, the lectin has antiviral
Antiviral drug
Antiviral drugs are a class of medication used specifically for treating viral infections. Like antibiotics for bacteria, specific antivirals are used for specific viruses...
properties: it inhibits the human immunodeficiency virus enzyme reverse transcriptase
Reverse transcriptase
In the fields of molecular biology and biochemistry, a reverse transcriptase, also known as RNA-dependent DNA polymerase, is a DNA polymerase enzyme that transcribes single-stranded RNA into single-stranded DNA. It also helps in the formation of a double helix DNA once the RNA has been reverse...
. Other studies suggest that B. edulis also has antiviral activity against Vaccinia
Vaccinia
Vaccinia virus is a large, complex, enveloped virus belonging to the poxvirus family. It has a linear, double-stranded DNA genome approximately 190 kbp in length, and which encodes for approximately 250 genes. The dimensions of the virion are roughly 360 × 270 × 250 nm, with a mass of...
virus and tobacco mosaic virus
Tobacco mosaic virus
Tobacco mosaic virus is a positive-sense single stranded RNA virus that infects plants, especially tobacco and other members of the family Solanaceae. The infection causes characteristic patterns on the leaves . TMV was the first virus to be discovered...
grown in culture. Antiviral compounds from mushrooms are a subject of interest in biomedical research for their potential to advance the knowledge of viral replication
Viral replication
Viral replication is the term used by virologists to describe the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. From the perspective of the virus, the purpose of viral replication is...
, and as new drugs in the treatment of viral disease.
The fruit bodies have a high antioxidative
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...
capacity, due probably to a combination of various organic acid
Organic acid
An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are relatively stronger acids. The relative stability of the conjugate...
s (such as oxalic
Oxalic acid
Oxalic acid is an organic compound with the formula H2C2O4. This colourless solid is a dicarboxylic acid. In terms of acid strength, it is about 3,000 times stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations...
, citric
Citric acid
Citric acid is a weak organic acid. It is a natural preservative/conservative and is also used to add an acidic, or sour, taste to foods and soft drinks...
, malic
Malic acid
Malic acid is an organic compound with the formula HO2CCH2CHOHCO2H. It is a dicarboxylic acid which is made by all living organisms, contributes to the pleasantly sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms , though only the L-isomer exists...
, succinic
Succinic acid
Succinic acid is a dicarboxylic acid. Succinate plays a biochemical role in the citric acid cycle. The name derives from Latin succinum, meaning amber, from which the acid may be obtained....
and fumaric acid
Fumaric acid
Fumaric acid or trans-butenedioic acid is the chemical compound with the formula HO2CCH=CHCO2H. This white crystalline compound is one of two isomeric unsaturated dicarboxylic acids, the other being maleic acid. In fumaric acid the carboxylic acid groups are trans and in maleic acid they are cis...
s), phenolic compounds
Polyphenol
Polyphenols are a structural class of natural, synthetic, and semisynthetic organic chemicals characterized by the presence of large multiples of phenol structural units...
and alkaloid
Alkaloid
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
s; the highest antioxidant activity is in the mushroom caps. Furthermore, fruit bodies were determined to have 528 mg of the antioxidant compound ergothioneine
Ergothioneine
Ergothioneine is a naturally occurring amino acid and is a thiourea derivative of histidine, containing a sulfur atom in the imidazole ring. This compound is made in rather few organisms, notably Actinobacteria and filamentous fungi. Ergothioneine was discovered in 1909 and named after the ergot...
per kilogram of fresh mushroom; this value was the highest among many food items tested in one study. Porcini were thought to have anti-cancer properties according to Hungarian research conducted in the 1950s, but later investigations in the United States did not support this.
External links
- Mushroom-Collecting.com King bolete