- Bolete Mushroom
- Penny Bun
The bolete mushroom is considered to be the type species of the genus Boletus. It is a basidiomycete fungus naturally found all around the continents of the Northern Hemisphere, in Europe, Asia and North America. Bolete mushroom also grows in southern Africa, New Zealand and Australia, but it is not native to the Southern Hemisphere where it was introduced by humans.
There are many types of bolete mushrooms. A large variety first classified in 2007 is the California king bolete (scientific Boletus edulis var. grandedulis). This species native to the western parts of North America has a dark color and a large size.
The best known European variety is Boletus edulis. It is usually associated with spruce trees but it also lives near hardwoods of various types. Bolete mushroom is easily identified by the large cap, with a brown color and a greasy clear surface.
The stem is very thick, finely reticulated and has a meaty texture. The pore area of young mushrooms is white, later the surface turns green or yellow and the pores themselves become visible. Unlike other mushrooms, it is very resilient to bruising and it can be sliced without changing its color by oxidation.
The bolete mushroom inhabits coniferous forests and deciduous ones, as well as plantations of trees. It forms a symbiotic ectomycorrhizal relation with the trees and layers of fungus envelop the underground roots. During summer and autumn, the mushroom becomes visible as the fruit bodies emerge on the surface and start producing spores.
The brown cap of bolete mushrooms is very large and examples with a weight of 3 kg and a diameter of 35 cm are known. A specific trait of all bolete species is the presence of tubes under the cap, instead of the usual gills. These pores allow spores to emerge, as soon as they become mature.
Stems are very thick and meaty, with a lighter color than the cap. They can be white or yellow, with a surface covered by reticulations, or a network of raised lines. The stipe has a height of about 25 cm and a thickness of 10 cm.
Bolete mushrooms have a very large edible cap; with a diameter between 7 and 30 cm. Young specimens have a convex cap, which becomes flatter at maturity. It has a brown or red color that fades towards the edges, which can be almost white.
The cap becomes darker in time and it is usually covered by a sticky layer. Compared to other mushrooms, it has a large stem relative to the size of the cap. Due to the unusual diameter, it resembles a club. The lower part is covered in irregular ridges, while the top one is finely reticulated.
Under the cap there is a network of small tubes with a depth of 1 or 2 cm. These produce the spores that propagate the mushroom and have a white color when immature, becoming yellow or green with age. The spores are very small and 2 or 3 of them are located on every millimetre of the surface.
Bruising doesn’t change their color, which is initially white, then yellow and finally brown as the mushroom ages. The pores of young specimens look like cotton, due to the mycelia that fills them.
Young mushrooms have thick and white flesh, with a firm texture. In time, the flesh becomes more and more spongy. Most mushrooms don’t change their color when cut but some can become brown or red. These mushrooms can grow to big sizes; mature ones weight around 1 kg.
A record example with a weight of 3.2 kg was found in 1995 on the Isle of Skye in Scotland. It had a cap diameter of 42 cm while the stem was 14 cm wide and 18 cm high. Another large mushroom was found in a Polish forest in 2013.
B. edulis is probably the safest of all wild mushrooms to pick and consume from the wild. The devil’s bolete (Rubroboletus satanas) is the only poisonous mushroom with a similar shape but the differences are quite obvious since the stem is red and any bruise gives it a blue color.
It is sometimes mistaken with Tylopilus felleus, which is not poisonous but the flesh is so bitter that it can’t be consumed. Real porcini mushrooms have a brown stalk covered in a white reticulated pattern resembling a net and white pores, while Tylopilus felleus has a white stalk and a dark reticulated pattern, as well as pink spores.
Tasting the flesh is the most conclusive test, since the one of the fake bolete will be extremely bitter and unpalatable. The smaller Gyroporus castaneus is also sometimes confused with a bolete, despite its brown stem.
The tiny spores have a size of 12 -17 by 5 -7 µm and their shape is either elliptical or similar to a spindle. The cells that produce spores, known as the basidia, are located on a layer of cells named the hymenium. This layer covers the tubes and the end part of every cell faces towards the tube centers.
Basidia cells have a size of 25 – 30 by 8 – 10 µm and thin walls, each one is usually attached to four spores. The hymenium also includes big sterile cells named cystidia, which balance humidity like some sort of air traps, by entering the lumen of the hymenium beyond the basidia.
A cystidia located on the face of a pore is named a pleurocystidia, which is a 30 – 45 by 7 – 10 µm cell with thin walls and a spindle-like shape. B. edulis doesn’t have hyphae with clamp connectors but the cells located on the edge of pores, named cheilocystidia, give the hymenium a stuffed appearance.
At the same time, bolete mushrooms are low in saturated and unsaturated fats but have a high amount of dietary fibers. Fibers make digestion more effective, preventing constipation and other similar issues. In addition, bolete mushrooms provide a type of natural proteins that are easily digested.
Bolete mushrooms are packed with natural antioxidants. These include vitamin C, several phenolic compounds, flavonoids and ergothinene. They also provide a sizeable amount of essential minerals like zinc, copper, iodine, selenium, manganese and even the rare molybdenum. Like other mushrooms, they include a small amount of vitamin D, which is rarely found in food.
This vitamin is usually produced by the action of sunlight and is needed for the metabolism of phosphate and calcium. The species provides large doses of riboflavin, niacin, thiamine, pantothenic acid, pyridoxine and all other elements of the B-complex vitamins. The extract of the bolete mushroom was found to improve immunity and reduce the risk of cancer.
Vitamin B6 is also part of the wider B complex and it is important for a robust immune system. It keeps lymph nodes healthy and speeds up the assimilation of carbohydrates, fats and amino acids, as well as balancing the level of sugars in the blood.
Folate, or vitamin B9, is mostly used by the liver, although it plays other roles as well. Vitamin B12 is used in the production of DNA and is needed for the neurological function. Vitamin B9 is also critical for pregnant women, in order to avoid birth defects and it is also heavily used by the nervous system and in the synthesis of red blood cells.
Bolete mushrooms also provide other key nutrients. Dietary fibers regulate digestion, preventing constipation and allowing us to extract more nutrients from food. Potassium is one of the most important minerals and it is needed for heart health, the production of proteins and the balance of fluids. A proper supply of potassium improves skeletal strength, prevents strokes and can balance blood pressure.
Zinc is another very important mineral that is involved in many functions such as digestion, immune reaction, energy metabolism and blood glucose balance. Copper is required for enzymatic reactions, healthy connective tissues, a healthy rate of growth in kids, as well as a regular heartbeat.
Bolete mushrooms can be prepared when fresh, in a variety of recipes. They can be stir-fried, grilled, sautéed, braised or marinated. A famous staple of Italian cuisine is risotto al porcini, which is a rice-based dish with sliced dried or fresh bolete mushrooms cooked with white wine as well as garlic, onion and parsley.
Sautéed boletes in oil or butter with garlic are served by most French restaurants. Small slices of these mushrooms are a great addition in many dishes, for example rice, pasta, sauces, stews, stir-fried recipes or soups.
Due to their large size, bolete caps can also be stuffed. Pizzas, pastries, pastas and potpies can benefit from the addition of bolete slices for an improved taste. Similar to other wild mushrooms, they pair very well in any recipe with poultry, seafood or lamb.
Since they don’t last long, you should consume boletes as soon as possible. If you plan to eat them later, there are several methods of preservation. Drying the boletes is the most common option in the USA. Before drying, cut the mushrooms along their whole length in slices not thicker than half an inch, include the stems as well.
Slices around 1/4-inch thick are recommended for storage inside the freezer in a special bag. They last at least 6 months, without losing their flavour. Unlike other mushrooms, boletes can also be pickled and are a popular snack at cocktail parties.
When you use dried boletes in the kitchen, remember that 3 ounces of dried boletes are the same as rehydrated mushrooms weighting about 1 pound. As for how long you should keep them in water for rehydration, the best chefs in the world have different opinions.
Soaking them for approximately 15 minutes in warm water seems to be the norm, since the heat speeds up the process. However, you have to consider how thick the slices are. Squeeze the excess water at the end but keep it for other uses, since it has a great flavour as well.
Dried boletes can cover other ingredients of soups, pastas or polentas due to their rich and powerful taste. The aroma is also present in your kitchen, every time you use them in cooking. It is actually so powerful that a pot used for cooking boletes will keep their flavour long after it was repeatedly washed.
After the bolete mushroom slices are fully soaked, you can cut them into smaller pieces. Larger pieces will have a stronger flavour than the small ones. A fast sauté in olive oil and butter is recommended by some top chefs before using the mushrooms as an ingredient.
The water that remains after soaking can be used to improve the taste of many dishes. Be careful to discard the remains that build up on the bottom and only use the most concentrated liquid.
Bolete mushroom is considered a delicacy all around the world and it is included in many recipes such as pastas, soups or risottos. Several cuisines praise it as a special ingredient. Bolete mushroom provides a great mix of nutrients, including vitamins, minerals, proteins and dietary fibers, while having a low content of carbohydrates and fats.
Despite its high commercial value, it is very difficult to cultivate. Bolete mushroom is harvested from the wild during the autumn in Southern, Central and Northern areas of Europe and exported all over the word, usually in dried and packaged form. Its flavour remains the same after rehydration and it can be used as such in cooking.
It is also one of the few mushrooms that can be preserved by pickling. It provides numerous bioactive organic compounds, such as phytochelatins, which boost the body’s ability to resist toxic heavy metals. It is also rich in antioxidants, a sugar binding protein, antivirals and ergosterol, which is a steroid derivative.