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Classification of fungi
Fungi are mostly classified in edible mushrooms, poisonous mushrooms and moulds. Between 70,000 and 100,000 species are known today. What is known as edible mushroom and such suited for consumption is in most fungi the fruiting body growing above earth with the typical mushroom form of stem or stipe and cap. Only few edible mushrooms such as truffles form a completely different fruiting body. Under the cap of mushrooms grow many papery ribs. These ribs form gills or lamellae (gilled mushrooms) or tubes (boletes). Within those gills or tubes are microscopically small spores. Spores, like seeds in higher plants, are a reproductive structure for dispersing and propagating the fungus. The stem of the fruiting body is supposed to elevate the cap so that the wind can pick up ripe seeds.
The underground part of most edible mushrooms consists of mats called mycelium. These mats can grow several meters in diameter around the fruiting body. They consist of many, microscopically thin threads called hyphae. Hyphae can be compared to roots in higher plants. They take in nutrients from the soil and transport them within the network.
Fungi are classified in the divisions or phyla of chytrids (bot.: Chytridiomycota), zygote fungi (bot.: Zygomycota), sac fungi (bot.: Ascomycota) and Higher fungi (bot.: Basidiomycota). Higher fungi include most edible fungi, among many others button mushrooms, porcini and chanterelles. Only few edible mushrooms, among them morels and truffles belong to the division of sac fungi.
Moulds (bot.: Myxomycota) are micro-organisms. Cultured moulds are grown indrustrially for the production of certain foods such as cheese, some sausage varieties, soy sauce, tempeh and pu-erh tea. The natural mould Botrytis cinerea, also called noble rot, grows on ripe grapes and is important for the production of certain wines.
Yeasts are used for the production of baked goods, bread, wine and beer.
Life of fungi
Fungi do not contain chlorophyll, therefore they cannot synthesise their energy through light, carbon dioxide and water, i.e. use photosynthesis. The metabolism of fungi is therefore dependant on organic matters of other organisms. Fungi feeding from dead organic matters are called saprotrophs (bot.: Saprophytes). Saprotrophs are responsible for the decomposition of dead organic matters. Fungi feeding from living organisms are called parasites. Among those parasites are many fungi detrimental to plants and causing extensive damage and loss to agriculture.
A third group to which most edible fungi belong are symbionts. Symbionts live in a symbiotic relationship with their host organism and may even improve the growth of their hosts. Symbiosis between fungi and plants is called mycorrhiza and has been described for the first time in 1885 by B. Frank studying wood flowers. Some estimates say that 80% of all plants live in mycorrhiza with fungi.
Nutrients in edible mushrooms
Nutrients in edible mushrooms vary between different mushroom varieties. The fruiting body contains 90% water on average, between 1.5 and 3% protein, and 3 to 5% glycogen and carbohydrates. They are a good source for minerals, potassium and phosphoric acid. Vitamin D, which is scarce in most vegetables, is relatively high in edible mushrooms, as well as vitamins of the B-group. The fruiting body of mushrooms often contains chitin and cellulose. Chitin is the main component of carapaces, exoskeletons and wings of insects. Both chitin and cellulose are hard to digest but enhance action of the bowels as dietary fibres.
How mushrooms are sold
Mushrooms are sold fresh, canned, frozen or dried (see: dried mushrooms).
Storage of mushrooms
Fresh mushrooms spoil fast and have to be eaten as soon as possible. They should not be stored wrapped in plastic but in a single layer on a plate in the refrigerator. They are best covered with a damp towel, which makes air circulation possible. This way undamaged, healthy and wormfree mushrooms can be stored for a few days.
Dried mushrooms should be stored dark, dry and in low air humidity. They are best kept in loosely filled vacuum bags. The drying prolongs the shelf life of mushrooms considerably. Though even when they are stored under perfect conditions mushrooms should not be kept longer than until the beginning of the next mushroom season.
Most mushroom poisonings occur because poisonous mushrooms are mistaken for edible ones by mushrooms gatherers. Because many edible mushrooms have toxic look-alikes even experienced mushroom gatherers are sometimes poisoned.
Edible mushrooms that have been stored too long may also be poisonous. Decomposition and the formation of toxic matters from the proteins contained in mushrooms are responsible for this. Food poisonings may be the consequence of consumption of spoiled edible mushrooms.
There are no reliable measures to test the poisonousness of mushrooms at home. Neither taste nor smell or colour of the mushrooms are safe indicators for edibility of a mushroom or a dish containing mushrooms. Spoiled mushrooms do not turn black when touched by silverware or onion as a popular myths claims. Animals are not suitable for testing mushroom dishes either because some toxins innocuous to animals might be deadly for humans. Only detailed knowledge of mushrooms and toxic look-alikes and proper storage of edible mushrooms prevent mushroom poisoning. When in doubt, mushrooms should never be eaten.
The first symptoms of mushroom poisoning may show minutes or as late as 24 hours after consumption. In rare cases they might show even several days later. Typical symptoms include: revulsion, panic attacks, cramps, unconsciousness, delirium, and others. A doctor should be seen immediately if a mushroom poisoning is suspected.
Usage and preparation of fungi
Fresh edible mushrooms should be cleaned before consumption. Dirt is removed with a brush or, if clinging, with a small sharp knife. The stem is shortened or removed - depending on the mushroom variety and usage. Then mushrooms are used whole or cut to specific size, again depending on the recipe. Most mushrooms have a very fine aromatic taste that should not be covered up by other ingredients when preparing mushroom dishes.
Dried mushrooms have to be used with caution as they may contain salmonellae. Dishes with dried mushrooms have to be thoroughly heated. General rules of hygiene are important when preparing dried mushrooms. The same rules as for the preparation of poultry apply.
Medical uses of fungi
Mushrooms are of great importance in naturopathy. In China some species have been used as medicine for many centuries. Shiitake (bot.: Lentinula edodes) for example has been used since the Ming dynasty (1368-1644) as an elixir for healing colds and strengthening the body's defences. For modern medicine fungi are also of great importance since for example penicillin is produced from the mould fungus Penicillium notatum.