The fungi kingdom is one of the five major kingdoms scientists use to categorize organisms and describe their relationship to one another. Included in the kingdom fungi are mushrooms, molds and yeast, all of which have been eaten for several thousand years. Although some types of fungus are poisonous to humans, there are several edible fungi that are eaten directly or used as a component of foods.
There are several different types of fungus: mushrooms, molds, yeasts and truffles; subtypes of each of these are edible. Molds, mushrooms and truffles are multicellular fungi that produce tiny spores that reproduce. Yeasts are single-cell fungi that reproduce without producing spores. Unlike plants, fungi are not able to convert sunlight into energy, so they need to absorb nutrients from their surroundings. Some fungi attach to the roots of plants to feed, and thus are considered parasites.
Mushrooms are one of the most familiar types of fungus used as food. The part that most people see growing is often the only part of the organism that projects up out of the ground, with the rest of the organism growing beneath the soil. Mushrooms can be purchased at grocery and specialty food stores. They can also be gathered in the wild, but this practice is not for people who cannot positively and accurately discriminate between poisonous and edible mushrooms. Three very common types of edible mushrooms are button mushrooms, available in most grocery stores across the U.S. in fresh and canned forms; the portabella mushroom, which is a very mature form of the button mushroom, with a meat-like texture; and the shiitake mushroom, which is native to China and Japan.
Although yeasts are often associated with infections, some types of yeast are edible and quite useful in food production. Baked bread that rises to be light and fluffy would not be possible without yeast. According to the University of Hawaii at Manoa, yeast was first used by Egyptians to make bread rise about 5,000 years ago. Additionally, the Egyptians were also the first to use yeast to make a then-novel alcoholic beverage called beer.
Some types of mold are used to flavor cheeses, which have been added to cheese for about 2,000 years, notes the University of Hawaii at Manoa. One of the most famous of the moldy cheeses is Roquefort, in which green-blue veins of mold grow and give it a very distinctive color, odor and flavor.
Truffles are a subterranean type of edible fungus that often resemble clumps of dirt. However, truffles are considered a delicacy by many, and their rarity makes them very expensive. Although humans cannot detect their distinctive odor, dogs and pigs can smell truffles from some distance away. Humans often use these animals as truffle hunters to locate these pricey rare foods.