All About the Amazing Oyster Mushroom, Including How to Prep and Use It in Your Cooking
Once upon a time, in the late 20th century, the only mushroom you could find in a U.S. supermarket was the diminutive button mushroom. After that, portobellos arrived in both macro and micro form, and then shiitakes crept in. But by the time the 2000s came around, there was a clear shift: The gourmet mushroom-growing business began to boom as technology to cultivate them evolved and demand grew. Fresh oyster mushrooms (species of Pleurotus), previously a wild-only edible fungus, are now within a curious cook's reach. They are delicious, nutritious, and readily available at major grocery chains as well as at farmers' markets. Their smooth clusters look unusual, and their texture is unfamiliar. How are oyster mushrooms cultivated, and what is the best way to use them? What parts of them do you eat, and do they have any health benefits? All good questions, with fascinating answers. Oyster mushrooms are magical (but...not in that way).
In the Wild
In the wild, oyster mushrooms grow in overlapping shelves on logs or living trees. They are saprotrophic, digesting organic matter, and they cause a white rot that kills hardwood trees (which they infect through a wound in the bark). Their stems are often lateral (growing to the side) and are short and stout. White gills extend partially down those stems. They are impervious to seasonal shifts and you may find them on a muggy summer afternoon or in the middle of winter, as long as there has been some rain.
Cultivated Oyster Mushrooms
Once cultivated only in East Asia (China still exports more oysters mushrooms than any other country), American production increased earlier this century as interest in oysters grew. Commercially-produced oyster mushrooms are grown from mycelium (interwoven, threadlike matter) that is propagated on a base of cereal grain. This mixture is called spawn and is used to inoculate the substrate (the organic material that the mushrooms feed on). They can grow on any organic matter that contains cellulose; in the U.S., the substrate is usually a mix of straw and cottonseed hulls packed into perforated bags. The bags are then placed in a warm, dark environment to incubate and begin the first phase of growth. After about two weeks, when the spawn has colonized the substrate, the bags are exposed to light, high humidity, and sometimes cooler temperatures. This provokes fruiting, when mushrooms form, starting as pinhead-sized caps. They are ready to harvest—in their characteristic, shelf-like clusters—after about a week.
What About the Colors?
Commercially grown oysters come in a rainbow of colors. They are the domesticated versions of wild oyster mushrooms that grow naturally in different climates. The so-called summer or phoenix oyster mushroom originates in subtropical and temperate forests and has white to tan caps. Pearl oysters are white to gray and prefer colder temperatures. Pink oyster mushrooms come from tropical regions; blue oysters are found throughout the Northern Hemisphere, and the golden oyster mushroom is native to eastern Russian, China, and Japan. Now, they're ours to grab at the grocery store or grow at home.
So, How Should I Eat Oyster Mushrooms?
Cooked oyster mushrooms have a savory flavor and a dense texture, making them a versatile ingredient. Know that because the cell walls of all raw mushrooms contain indigestible chitin, which is broken down by heat, oyster mushrooms should be cooked. Chitin can also provoke an inflammatory reaction. Oysters also contain a protein called ostreolysin, which can be toxic unless the mushrooms are cooked at temperatures above 140 degrees Fahrenheit, according to mushroom guru Paul Stamets. Small oyster mushrooms can be cooked whole, or dropped into soup (where they are slippery and, well, oyster-like), while large ones can be sliced or seared entire for a wonderful vegan steak. When sautéed, their flavor concentrates and becomes rich. Cook them gently in butter or your favorite oil, taste, and season lightly (as they caramelize their umami qualities become more pronounced). Pan-cooked, they are excellent sandwich fillers, egg-toppings, and delicious substitutes for ground meat in dishes ranging from mapo tofu to lasagna. Oyster mushroom stems tend to be tough but they make an excellent mushroom broth.
And if you love bacon but tend to follow a vegan diet, the New York-based mycelium-innovator Ecovative and their food partner have developed a vegan bacon called MyBacon, based on oyster mushrooms, rather than meat. Still produced on a small scale for sale in Albany, New York, they are expanding to increase production to meet national demand this year. While traditional medicine has long touted the health benefits of mushrooms, science is still catching up in terms of proven results. Still, oyster mushrooms are demonstrably antibiotic, and are associated with antiviral activity, and cholesterol-limiting properties.
Some Unusual and Amazing Oyster Mushroom Facts
Fun fact: Oyster mushrooms are actually carnivorous! They ensnare and digest nematodes (tiny worms), which can make them higher in protein than you'd think. Their cellulose-digesting enzymes mean they are exceptional mycoremediators, able to absorb, sequester, or destroy pollutants, and potentially useful in clean-ups ranging from clearing oil spills to breaking down disposable diapers. And they convert substrates like straw into water in their fruiting bodies, making them very interesting in a world facing clean water insecurity.
If that doesn't make you respect your oyster mushroom dinner, we have failed. Bon appétit!