The Wonderful World of Fungi
Part XVIII – Division Basidiomycota – Fascinating Members: Edible Mushrooms
By: H. Wayne Shew, Ph.D.
NAB Certified Pollen Counter
AAAC Collection Station—Birmingham, Alabama
It has been some time since I wrote about the group of fungi called basidiomycetes and some of the incredibly fascinating members of this division or phylum of organisms. I first want to give a brief description of the taxonomy of this phylum and some of the groups of fungi included there before discussing in more detail some of the edible fungi in this group.
The phylum Basidiomycota (referred to in my blogs as basidiomycetes) has three subdivisions: Agaricomycotina, Pucciniomycotina, and Ustilaginomycotina. The Agaricomycotina include the fungi most people are familiar with which includes the mushrooms, puffballs, bracket fungi and other polypore fungi, earth stars, boletes, chanterelles, stinkhorns, and jelly fungi. The largest percentage of these fungi are placed in the class Agaricomycetes, while a very small percentage are placed in the classes Tremellomycetes and Dacrymycetes, the jelly fungi. Jelly fungi have gelatinous fruiting bodies that are most conspicuous following rain showers. The fungi absorb moisture and swell, developing the gelatinous texture which gives them the name jelly fungi.
Members of the subdivision Agaricomycotina produce sexual spores called basidiospores on club-shaped structures called basidia, structures that vary in shape and which may or may not possess septa. (Note: Basidiospores can trigger allergic reactions in some individuals when the spores are released and become part of the aerospora. In addition, some individuals can suffer from contact dermatitis following contact with certain species of Basidiomycetes. Susceptible individuals having fungal allergic reactions should always be aware of possible fungal allergens in the environment and how best to avoid them. A future blog will address basidiospore allergy.) Most of the fungi in this subdivision were traditionally referred to as Hymenomycetes. Fungi formerly placed in this traditional taxon form their basidia on the outer surface(s) of the fruiting bodies, but the term Hymenomycetes is no longer taxonomically relevant. Other members of the Agaricomycotina subdivision were traditionally referred to as gasteroid fungi (obsolete class Gasteromycetes) because they produced spores inside their basidiocarps instead of on the outer surface. A great way of seeing the traditional way that the Basidiomycota division was divided into taxa is to access, https://www.thefreedictionary.com/Basidiomycota.
The goal of this blog is to consider fungi in the Agaricomycotina taxon that are edible; those that may be collected by individuals in small numbers and eaten but which are not commercially significant, and those that are commercially important because of the large numbers grown and consumed by humans.
Edible fungi are “fleshy” fungi whose fruiting bodies are collected and eaten raw or cooked. These fungi may be cooked and eaten as a side dish, but more often are part of a dish that contains other ingredients. The fungal fruiting bodies may grow below ground, but most of the edible fungi produce above ground fruiting structures. Edible fungi may be consumed for their nutritional value but most are eaten for their culinary value. A few edible fungi are consumed as part of folk medicine and would thus more properly be called medicinal fungi. Some fungi are consumed for recreational purposes because of the psychological (hallucinogenic) effects they produce. Both medicinal and hallucinogenic fungi are not eaten in large amounts and are thus not commonly used as food. (Note: there are edible fungi that are ascomycetes not basidiomycetes, for example, truffles and morels, and these will not be discussed in this blog.)
A short disclaimer: There are huge numbers of fungal species that are edible. These can be found either in your friendly neighborhood supermarket in the produce section, or collected in the fields and forests nearby through foraging. Even though people have been collecting and eating mushrooms for thousands of years, you should not go out hunting for mushrooms on your own unless you are an experienced mycologist. There are enough poisonous species that look similar to savory, edible ones that it isn’t worth your health or life to risk collecting wild mushrooms for haute cuisine that could instead lead to “halt” cuisine.
A list and brief description of some of the more commonly cultivated mushrooms are given below:
This mushroom is the most commonly cultivated mushroom and is grown commercially throughout the world. It dominates the market in North America and Europe, and makes up about 15% of global mushroom production. The mushrooms are cultivated on substrates hat include horse manure, wheat straw, corn cobs, and other plant wastes as well as some animal wastes, for example, feather meal and chicken manure. When young, this mushroom is referred to as the button mushroom, or cultivated mushroom, or common mushroom; I usually refer to it as the pizza mushroom. The young fruiting bodies are white or light brown and have caps that are typically in the quarter to half-dollar size range. They have a mild, pleasing flavor and are quite versatile in their culinary uses—eaten raw, sautéed, and as part of various dishes. You can also find them canned and dried. When mature these mushrooms are called portobello mushrooms. They are usually 2-4 inches in diameter with dark gills under a dark brown cap. These mushrooms have a meat-like flavor and substantial texture and can be eaten as a portobella sandwich. They may be cooked whole or sliced; fried, sautéed, grilled, or baked.
This mushroom is commonly called Shiitake. It is popular in U. S. markets and is considered by some to be the king of commercial mushrooms. It is also common in Asian markets, being produced in China, Korea, and Japan. The mushroom has a cap that is black when young and changes to dark brown to light brown with age. It is 5-25 cm in diameter and has a convex shape at maturity. The gills are white and entire (no serrations) initially but become serrated with age. The stems are fibrous and tough. This species is estimated to make up 10% of the world production of cultivated mushrooms. Shiitake is cultivated much like Pleurotus ostreatus, that is, outside on oak logs, or inside using sterilized sawdust in polypropylene bags. These mushrooms have a good shelf life and can be kept for a month or more when refrigerated in paper bags or cartons. The mushrooms can also be dried and kept for extended periods of time. The rehydrated mushrooms have a more intense flavor than fresh ones. If you purchase dried Shiitake mushrooms, be sure to check the source since those imported from the far east can be contaminated with pesticides and heavy metals.
Pleurotus ostreatus (and other species of Pleurotus)
The common name is oyster mushroom. This is considered by many to be the easiest of the mushrooms to cultivate. Hence, it is a great one for novice mushroom cultivators to begin their experience into growing mushrooms for eating and/or sales to local establishments. The oyster mushrooms are very common in Asian markets and is listed as the second most important mushrooms in world-wide production, making up some 25% of the total world production of mushrooms. Several species of Pleurotus can be grown on high carbon materials such as straw or newspaper. (Wild species of Pleurotus are usually found growing on wood.)
The Maitake mushroom is also known as Hen-of-the-woods. It can be grown outdoors on logs or indoors on sterilized sawdust. Unlike the mushrooms described above, the Maitake mushroom is a polypore rather than a gilled mushroom. Polypore fungi have pores that bear the reproductive structures called basidia. The basidia line the interior of these pores rather than covering the surface of structures that resemble gills as is found in the gill fungi. The fungus is a bracket fungus and is native to China, parts of Japan, and North America. G. frondosa is perennial and can grow in the same location for many years. The fruiting body of this fungus grows from an underground structure called a sclerotium. The fruiting body can get quite large, as much as 100 cm, and consists of a cluster of caps which grow very close together. As with other bracket fungi, the Maitake mushroom becomes inedible when old because the stalk and caps become tough and are unsuitable for eating.
Auricularia auricula & A. polytricha
The common name for these fungi is ear fungus because of the shape of the mature fruiting bodies. These fungi are referred to as jelly fungi because of their texture when present in wet conditions such as after a rainstorm. During dry conditions the fungi lose their jelly-like consistency and become tough, a texture more like stiff paper or thin plastic. The fruiting bodies are brown to reddish-brown in color when wet. These two species of Auricularia are the most popular members of the jelly fungi that are consumed. The fungi grow as saprophytes on logs in nature. They can be cultivated on logs but are more commonly grown commercially in a polypropylene bag that has a filter to prevent contamination of the sterilized sawdust-grain medium on which the ear fungi grow.
There are numerous websites showing what the above fungi look like; I suggest you check them out. These fungi are all available commercially and thus remove the concern about the safety of eating them, at least if they are purchased from reputable mushroom growers. Consider giving some of these fungi a try in the near future and get a taste of some of the unusual and pleasant flavors of fungal fruiting bodies.
I will address some of the edible basidiomycetes that are normally not cultivated but are routinely collected and eaten by mycophagists in a subsequent blog. Happy eating.