Gyromitra esculenta

The False morel (Gyromitra esculenta), also known by a variety of common names such as Lorchel, Brain fungus, Red mushroom or Beefsteak mushroom, is a poisonous ascomycete fungus somewhat similar in appearance to the "true" morel (Morchella sp.). False morels are deadly poisonous when raw, but they are edible if parboiled.

Aficionados of false morels describe them as one of the choicest of all culinary mushrooms. They are popular in Scandinavia, where they are sold commercially, and the upper Great Lakes region of North America. In Finland, false morels may even be sold fresh, but must always be accompanied by conspicuous warning signs as well as instructions on how to prepare them correctly. Properly prepared, there is no statistical evidence that eating false morels would be particularly dangerous: even though the mushrooms are widely consumed in Finland, between 1885 and 1988 only four cases of fatal gyromitrin poisoning were recorded, all of them caused by eating the mushrooms raw. On the other hand, the Finnish authorities strongly advise against eating false morels daily, since gyromitrin may accumulate in the body.

Description
While false morels somewhat resemble True morels, in that both are brown and wrinkly, the two are quite easily distinguished with some practice. False morels are irregularly shaped, resembling a brown brain, while the true morel is more symmetric and looks more like a pitted gray, tan, or brown sponge. False morels (G. esculenta) are also generally darker than true morels. False morels also generally have solid "stems", whereas true morels are hollow.

Classification
The name False morel is also applied to other species of the genus Gyromitra, such as G. infula (elfin saddle), G. caroliniana and G. gigas (Snow morel). While some of these species contain little or no gyromitrin, many sources recommend treating them all as poisonous, since their similar appearance and significant intraspecific variation can make reliable identification difficult. The name is also sometimes used for mushrooms of the genus Verpa, such as V. bohemica and V. conica, also known as early morels or thimble morels.

Distribution and habitat
Gyromitra esculenta grows on sandy woodlands, both on coniferous and deciduous, preferring the former. It is an early mushroom, and hunting period is from April to July. The mushroom usually grows only on places, where the surface of the ground has been broken, such as openings, rivulets, washes, timber clearings, plowed openings, forest fire clearings, roadsides etc. The growth can be promoted by breaking the terrain further in places where false morel is known to grow. False morels are not suggested to inexperienced fungophiles, though, since they require special treatment to become edible.

Toxicity
False morels contain gyromitrin, a volatile water-soluble hydrazine compound that decomposes in the body into methyl hydrazine. It acts as a hemolytic toxin as well as damaging the liver and the central nervous system. Due to its volatility, even the mere presence of fresh false morels in a poorly ventilated space may cause gyromitrin poisoning symptoms such as headache, dizziness and nausea. Consuming raw or incorrectly prepared false morels can result in catastrophic liver failure and death.

Geographical Variation
The edibility of the false morels is disputed and opinions vary from country to country. Some varieties of false morels are consumed, but all false morels contain various amounts of gyromitrin. In some countries like Spain, especially in the eastern Pyrenees, they are traditionally considered a delicacy, and many people report consuming them for many years with no ill effects. To that end, it is a very rare mushroom, and not likely to be consumed more that once a year. It has been confirmed that all false morels contain varying amounts of gyromitrin, but the amount present can be significantly reduced through parboiling (leaching). Gyromitrin is a cumulative poison, and consuming even a small amount over years can still have negative consequences later on. However, it is not known how the initial amount of gyromitrin depends on the concrete species, and it is known that it depends widely on the terrain and other environmental factors. Even following the recommending procedures in preparing a false morel, it remains a potentially dangerous activity as one can never be certain as to how much gyromitrin is contained within. As a result, all false morels are listed as toxic and inedible in mushroom lists published by the Catalan Government in Spain, even though some people do consume some of them.

Furthermore, it may be possible for American false morels to contain more toxin than Scandinavian specimens. The Finnish authorities suggest picking false morels in a bag separate from other mushrooms, which is to be washed immediately after use. If you do your mushroom hunting by car, false morels should be stored in trunk, since they can emit gyromitrin in the cabin and cause poisoning symptoms to the driver.

Preparation
To render false morels edible most of the gyromitrin must be removed. The recommended procedure involves cutting the mushrooms into small pieces and boiling them twice in copious water (at least 3 parts water to one part chopped mushrooms) for at least five minutes. The gyromitrin will dissolve in the water, which must be discarded after each boiling. Some of the gyromitrin will also evaporate, producing toxic fumes. This process is called parboiling, and it is to be done with good ventilation. If boiling the mushrooms indoors, one should therefore take care to ensure adequate ventilation, and, if symptoms of gyromitrin poisoning appear, immediately seek fresh air. As unit operation in chemical engineering the parboiling equals leaching; the gyromitrin is leached off the mushrooms. As the rule of thumb each round of parboiling reduces the gyromitrin contents to a tenth.

Each parboiling round must be done on different batches of water. Since the gyromitrin is leached into the water, it will remain there. Therefore the used water must always be discarded and replaced with fresh water.

Even after boiling, small amounts of gyromitrin remain in the mushrooms. While these small quantities will not cause noticeable symptoms to most people, some people may be hypersensitive to the toxin, and can become seriously ill from eating even properly prepared false morels. Gyromitrin sensitivity is apparently not a hereditary matter, further confusing the question of toxicity. Some sources claim false morel toxicity to be purely a matter of luck and/or individual variation, but these often fail to make a distinction between raw and prepared mushrooms, or cite incorrect methods of preparation.

According to Finnish law, selling and purchasing fresh false morels is legal, but the mushrooms must always be accompanied with legally prescribed preparation instructions. False morels are also sold prepared and canned, in which case they are ready to be used.

Carcinogenicity
There is also evidence that even small amounts of gyromitrin may have a cumulative carcinogenic effect. Thus it may not be advisable to consume even properly treated false morels too frequently, and many sources advise completely against consuming false morels at all.