Oyster Mushrooms
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Oyster Mushrooms (Pleurotus ostreatus), also known as Tree Oyster Mushrooms, Tree Oysters, Oyster Shelf Mushrooms, Pearl Oyster Mushrooms, Abalone Mushrooms (wrongly and confusingly since there are also two different types of different Abalone Mushrooms), Pleurotte (in French), Hiratake (means "Flat Mushroom" in Japanese), and Straw Mushrooms (not to be confused with Paddy Straw Mushrooms), are an edible fungus and the third most consumed Mushroom in the world (behind Button Mushrooms and Shiitake Mushrooms).

The name “pleurotus” means “sideways” in Latin and is apt because Oyster Mushrooms grow sideways out of decaying portions of living hardwood trees. “Ostreatus” means “oyster” in Latin and is descriptive because the mushrooms are the same shape and color as the bivalve Oysters from the ocean. It is from “Ostreatus that Oyster Mushrooms get their name, and it is a fitting one because many people believe that Oyster Mushrooms also have a taste and fragrance reminiscent of saltwater Oysters.

The Oyster Mushroom was first described scientifically in 1775 by Dutch naturalist Nikolaus Joseph Freiherr von Jacquin (1727 - 1817) and named Agaricus ostreatus. In the early days of taxonomy, most of the gilled mushrooms were included in the genus Agaricus, which contains Button Mushrooms. In 1871 German mycologist Paul Kummer invented a new genus “Pleurotus” to describe Oyster Mushrooms. They have been there ever since.

Oyster mushrooms don’t fit the model, of the typical Mushroom (sporophore) and with a Cap (Pileus) and a Stem or Stalk (Stipe). Unlike most mushrooms which grow up from a stem, Oyster Mushrooms have a lateral attachment to their growth medium and grow sideways out of the host (tree, fallen log, sawdust block, etc.). When viewed in nature they appear as if the Oyster Mushroom had been thrown cap first, like a ninja throwing star, into the growing substrate. Consequently, most Oyster Mushroom varieties don’t have a stem. If they do have one, it is usually short, thick, tough and off center.

The Oyster Mushroom has a broad, fanned, oyster-shaped cap spanning 2-10 inches (5–25 cm) with an in-rolled edge that is somewhat lobed or wavy and ranges from white to gray or tan to dark brown.

The flesh of the Oyster Mushroom is white, firm, and varies in thickness depending on the arrangement of the stem. The Oyster Mushroom’s gills (under the cap) are white to cream colored. As the Oyster Mushrooms grow larger they get “meatier” but lose flavor and their delicate texture.

Oyster Mushrooms are found growing all over the world, in areas where there are forests and a climate that has both rain and moderate temperatures. They can be found growing on hardwood, willows and conifers, most often on decaying or dead wood.

Though Smart Kitchen does not advise it, Oyster Mushrooms are widely foraged, even by novice mushroom hunters who take a risk. Unless you are an expert, or foraging with an expert, we vote against guide book foraging. 

Season

Oyster Mushrooms are now cultivated and thus grown commercially all year. Because they are harvested daily, grocery shoppers don’t have to worry about any “seasonality.”

If you had to search for a season for wild Oyster Mushrooms in North America, it would late fall through winter in North America, though in warmer climates they can be found all year. Pleurotus Pulmonarius, a close oyster mushroom cousin, that is edible and often confused for an Oyster Mushroom, fruits from mid-summer through early fall.

Availability

With Oyster Mushrooms grown in natural and controlled environments throughout the world today, fresh Oyster Mushrooms can generally be found in American grocery stores year around. Dried whole Oyster Mushrooms are also widely available and are a perfect, more economic substitute for fresh Oyster Mushrooms once you rehydrate them. Smart Kitchen has an Exercise on Rehydrating Mushrooms.

Cultivation

Oyster Mushrooms are a fungus and not technically plants. As a distinct organism, with unique characteristics, they require different growing conditions than a run-of-the-mill garden Vegetable we are used to tending. First of all, Oyster Mushrooms don’t create their own food from soil and sunlight through photosynthesis like plants. Instead they feed off of existing organic matter which makes them “heterotrophs.”

In the case of Oyster Mushrooms, specifically, they are “saprotrophs,” and primary decomposers of dead or decaying cellulose material. They don’t need composting like Button Mushrooms and do best growing outdoors on wood or indoors on composite blocks of sawdust, even chopped, sterilized straw. Oyster Mushrooms take about two weeks to spawn.

Though we desire the Mushroom Caps and Mushroom Stems, the bulk of the Pleurotus ostreatus mushroom fungus organism, the mycelium, tends to grow out of sight. It is there behind the bark, in its vegetative state, even when we don’t see any Mushrooms sprouting from a tree. Environmental cues, such as cold or precipitation, trigger the Mushroom to go into a reproductive state and send up mushrooms (also called fruiting bodies) to spread spores. This is why we see so many Mushrooms sprout up after a rain.

The fleshy fruit of the fungus is the Mushroom that we enjoy. Its purpose is to act as a spore producer to send out reproductive spores into the environment. Because of their reproductive role, Scientists call the sprouting, spore-firing, Mushroom a “Sporophore,” which translates from the Greek as a “Spore Producer.”

With the scientific terms it may be a bit confusing. Put more simply the edible Shiitake Mushrooms that we fancy are analogous to the apples of an apple tree. They are the fruit of the larger fungus. Instead of seeds, Mushrooms have spores.

When seen in the wild, Oyster Mushrooms may appear to be parasitic and attacking their hosts, but they are actually saprophytic, meaning they consume material that is already dead or dying. That portion of the tree which supports Oyster Mushrooms is therefore not as healthy as it appears and the Oyster Mushrooms is not killing the tree but doing the forest a service by decomposing the dead or decaying wood, and returning minerals and nutrients to the environment.

Mushrooms tend to prefer moist environments (95-100% humidity) and can grow quickly, especially after heavy rains.  Oyster Mushrooms can be found naturally almost all over the globe, wherever there is a forest with a perfect balance of rain and moderate temperature. Surprisingly, they are not naturally found in the Pacific Northwest, where its cousins Pleurotus pulmonarius and Pleurotus populinus dominate.

In nature, Oyster Mushrooms often appear to be growing right out of the side of a hardwood or coniferous tree, as though their caps were pushing out sideways from the trunks. If there is a stem, it is usually very small. They grow in clusters and in a variety of colors.

Oyster Mushrooms have been husbanded by Asian farmers for centuries but they were first “cultivated” in Germany during WWI as a subsistence measure. Because they are so easy to grow, they are now harvested all over the world. They can be raised, without much assistance at all, on any substrate composed of cellulose such as sawdust, chopped straw, waste husks / hulls, coffee grounds, newspaper, corn husks, even toilet paper rolls. Sterilizing the substrate is good but Oyster Mushrooms are very strong competitors and should be able to beat out all comers. Oyster Mushrooms are even carnivorous, able to kill and digest nematode worms. In fact, the North American Mycological Association labels Oyster Mushrooms as the easiest for home cultivators to grow and recommends them for beginners.

Inoculating a fallen log with Oyster Mushroom spawn is one way to go. Another choice is to use a prepared sawdust block or sterilized, chopped straw (wheat or other grains). Submerging the straw in hot water over 160˚ F (71° C) for an hour or so and then draining and drying will yield sterilized straw. The straw can be inoculated with Oyster Mushroom spawn and then stuffed into a plastic bag. Punch some holes into the bag to promote air exchange and to make openings for the Oyster Mushrooms to emerge. When they do arrive, Oyster Mushrooms are a little fragile, and should be handled carefully.

Though we discourage it, Oyster Mushrooms may be foraged. There are plenty of guides to help people determine which wild fungi are edible Oyster Mushrooms. If you decide to take this dangerous route, make sure to have an experienced person guide you. Double-check what you’ve picked before eating it.  For us, good grocery stores with interesting, revolving selections are the perfect foraging grounds, without the good walk or any of the risks.

Many vendors sell Oyster Mushroom Growing Kits for home users aiming to experiment. There is also a good book by Paul Stamet called “The Mushroom Cultivator: A Practical Guide to Growing Mushrooms at Home.” If you want to grow Mushrooms in a larger way, Paul Stamet’s other major work: “Growing Gourmet and Medicinal Mushrooms“ is very helpful. These last three links go offsite to Amazon.

Production

Oyster Mushrooms have been husbanded by Asian farmers for centuries but the modern Oyster Mushrooms cultivation process is relatively new, especially as compared to the cultivation of Shiitake Mushrooms and Button Mushrooms.

Oyster Mushrooms were first “cultivated” in the modern sense in Germany during WWI as a subsistence measure. Because they are so easy to grow, they are now harvested all over the world. They can be raised, without much assistance at all, on any substrate composed of cellulose such as sawdust, chopped straw, waste husks/hulls, coffee grounds, newspaper, corn husks, even toilet paper rolls. Sterilizing the substrate is good but Oyster Mushrooms are very strong competitors and should be able to beat out all comers. Oyster Mushrooms are even carnivorous, able to kill and digest nematode worms.

Oyster Mushrooms are the third largest crop of cultivated mushrooms by volume and China produces more than 85% of them.

Like the bulk of specialty mushrooms that are primary decomposers, most Oyster Mushrooms are grown commercially in long bags filled with straw or on sterilized compressed sawdust blocks packed in poly bags.

Once prepared, the substrate is inoculated with Oyster Mushroom spawn and placed in humid, environmentally controlled rooms in mushroom houses. After about two weeks of growth (various Oyster Mushroom strains need different lengths of time) the mycelium has done its work. The Oyster Mushrooms begin to grow out of holes in the plastic bag. The Oyster Mushrooms emerge from the synthetic substrate remarkably clean and are picked by hand. Harvesters grab a handful, pull and twist gently to release the Mushroom. They trim the stumps with a knife and grade them according to size and quality. A good harvester can pick up to 100 pounds (45 kg) an hour.

The modern Oyster Mushroom growing cycle (from spawn to final harvesting) takes about three to four weeks. If straw is used as a growing medium, the substrate can be used as fertilizer after mushroom production is completed.

Varieties

The Oyster Mushroom, also known as the Tree Oyster Mushroom that we see in stores in North America usually has an off-white colored stems with a beige to golden brown mushroom cap.

There are some other varieties though that pinkish or gray to light blue in color. These are called, respectively Pink Oyster Mushrooms (Pleurotus djamor) and Gray or Blue Oyster Mushrooms.  There are even some newer breeds of Oyster Mushrooms that are yellow or white.

There are also some edible Oyster Mushroom cousins. One such cousin is Pleurotus pulmonarius, more commonly called the Indian Oyster Mushroom, Italian Oyster Mushroom, Phoenix Mushroom or Lung Mushroom. They are very similar to Oyster Mushrooms but they have a stem and their mushroom caps are much smaller and paler than those on traditional Oyster Mushrooms. They also like warmer climates and have a later season.

Other, cousins are the King Oyster Mushroom (Pleurotus eryngii), the Branched Oyster Mushroom (Pleurotus cornucopiae), the Golden Oyster Mushroom (Pleurotus citrinopileatus),  the Tarragon Oyster Mushroom (Pleurotus euosmus), one of the  Abalone Mushrooms (Pleurotus abalonus), the other Abalone Mushroom (Pleurotus cystidiosus), and the Brown Oyster Mushroom (Pleurotus australis).

Purchasing

Oyster Mushrooms can be found in many local grocery stores in various forms including: Fresh Mushrooms (whole & prepped), Dried Mushrooms and Canned Mushrooms and Frozen Mushrooms. In general Fresh mushrooms have better texture and dried mushrooms have better, more concentrated flavor.

Fresh Oyster Mushrooms

Select fresh, young Oyster Mushrooms in prime condition, with broad, fleshy, darker caps with smooth, intact edges. Oyster Mushrooms lose color as they mature. In general, if the Oyster Mushrooms are from the same grower, the whiter the Oyster Mushroom Cap, the older, and tougher, they are. Also, if they are picked at an older age, the flesh can become more acrid and unpleasant.

Look under the Mushroom Cap. Is there a tough woody stem, that is not useful? Oyster Mushrooms grow from their sides and should have at most a minimal, off center stem. Why pay for something by the pound, like the stem that you will in all likelihood discard. No look under the Mushroom Cap. Oyster Mushrooms don’t have a “ring” protecting the Gills, like many other Mushroom species. The Gills on fresh Oyster Mushrooms should be intact and clear.

You may sometimes see fresh Oyster Mushrooms packed in their natural clumps instead of as individual mushrooms. Because Oyster Mushrooms are so fragile, the clumps lend some protection to the mushrooms while they are in transit.

Because they are very moist (about 90% water), the Oyster Mushrooms should appear and feel “springy,” that is firm and dry, without actually being dry or shriveled.

Aroma can also help you make better Oyster Mushroom purchasing decisions. Good, fresh Mushrooms will smell earthy. Oyster Mushrooms have a mild fragrance as compared to some other mushrooms, but the stronger the earthiness, the more flavor the Mushroom contains. Sour or fishy smelling Mushrooms should be avoided. Mold growth, bruising and sliminess are other definite signs that the Mushrooms are bad.

We tend to avoid buying pre-sliced, fresh Mushrooms because it is harder to tell how many mushroom caps you are getting. This can be a problem if a particular recipes calls for mushrooms by the count (the certain number of whole mushrooms) not by volume or weight. Also cutting into the product in a factory someplace starts the clock running on moisture loss. We can’t know how long the Oyster Mushrooms have been in transit.

Dried Oyster Mushrooms

For years, the odds were that you would only find Oyster Mushrooms in the United States canned or in their dried form. Today, the two forms can co-exist at retail where Dried Oyster Mushrooms are normally the most economical option. They also have a more concentrated mushroom-flavor. They have a good shelf life and are very convenient to use at home, if you plan ahead a little bit.

When purchasing Dried Oyster Mushrooms, look for a well-sealed package without any visible moisture, or mold, inside.  We have been able to find some deals on Oyster Mushrooms Online with reliable suppliers through Amazon. The link goes to Amazon.

In the United States, Oyster Mushrooms are also sold as extracts and dietary supplements.

Storage

Within the perishable world of Mushrooms, Oyster Mushrooms are fairly robust. They don’t bruise easily and have a decent shelf life even when fresh. Even so, excessive moisture degrades fresh Oyster Mushrooms and can make them soggy. Proper storage and handling will help you make the most of your Oyster Mushrooms.

When brought home from the store they should be stored in their original cardboard container on a shelf in the refrigerator. If you want to remove the plastic wrap, if any, and cover the Oyster Mushrooms with a dry paper towel that is fine. Placing them under wax paper, in a paper bag or in a Vegetable Bag is good as well. All of these choices allow air to circulate.

We don’t recommend using the higher humidity crisper drawer for moisture-sensitive Mushrooms. Stored as described above, Fresh Oyster Mushrooms should last about 1-2 weeks in the refrigerator. Stored at room temperature they will only last a day or so. Because of their moisture content, we don’t suggest freezing fresh Oyster Mushrooms at home.

If you found a great deal and want to store an abundance of fresh Oyster Mushrooms, you can Slice them and dry them at home in a Dehydrator. Dried Mushrooms should be stored in an airtight container in a cool dark place such as a cabinet or pantry. Stored this way they can last up to a year, maybe two. They can last even longer if they are dehydrated and then frozen. Another option would be to cook them first and then freeze them. Don’t forget that Dried Mushrooms will need to be Rehydrated before use.

To preserve, sauté them with butter or oil and then freeze them. Oyster mushrooms dehydrate rapidly and can be used in their dry state without re-hydrating.

Culinary Uses

Oyster Mushrooms have a mild, woodsy, initial taste with an earthy, bittersweet aftertaste. The taste is almost in the same realm as Anise. Some cooks claim that Oyster Mushrooms smell and taste like the salt water Oysters that they resemble. We understand the argument and think it is a stretch, but a defensible one.

The first thing to know about Oyster Mushrooms in the kitchen is that they should always be cooked before consumption. They contain a novel, heat sensitive hemolytic protein called “ostreolysin" which can be toxic unless it is destroyed by cooking temperatures above 140˚ F (60° C). Cooking will also break down cellular walls and release some of the nutritional benefits of Oyster Mushrooms.

Cooked Oyster Mushrooms are completely edible* (both Cap & Stalk). Cooked through they are less rigid than other Mushrooms but they have a firm bite that adds body and subtle mushroom flavor to dishes and Sauces. They are meaty and can stand up to almost any dish/flavor.

Younger Oyster Mushrooms are more tender than older specimens. If they are picked at an older age, the flesh can become tougher and meatier. The flavor also becomes more acrid and unpleasant with maturation.

Oyster mushrooms are fragile, and should be handled carefully. They should be used as soon as practicable to maximize their potential. Because of their delicacy, they tend to cook quickly. We add Oyster Mushrooms to any cooking process in the very late stages so that they don’t suffer from too much exposure to cooking heat. If overcooked they will become rubbery and lose flavor. They are also very porous, and can pick up surrounding tastes.

On Smart Kitchen’s Home Plate Oyster Mushrooms are Cooked, Tender, Thin, Moist and Lean (C, T1, T3, M, L).

Oyster Mushrooms are often associated with Asian Cuisine (primarily Japanese Cuisine, Korean Cuisine and Chinese Cuisine) but also feature in Indian Cuisine (primarily around Kerala) and have become more widely adopted as their availability and price has improved in the last few decades.

These cooked Mushrooms can then be eaten by themselves, as a Side Dish, used as a Garnish or added to other already cooked dishes such as Pastas, Hamburgers, Sandwiches, Sauces, and many of the uses listed above for raw Mushrooms. Also Oyster Mushrooms are versatile and substitute well into almost any other Mushroom recipe.

In the kitchens of America, Oyster Mushrooms are most commonly found in Soups and Stir-Frys though they are also used in Quiches or Omelets. How you use your imagination is really the only limiting factor.

Smart Kitchen’s Recipe section has a number of Mushroom recipes that work well with Oyster Mushrooms such as: Savory Oyster Mushroom Fritters, Batter Fried Oyster Mushrooms, Oyster Mushroom Baked Rice, Oyster Mushroom Fritatta and Mock Abalone.

Portion Size

Allow 1-2 T of Oyster Mushroom per person.

Substitutes

Depending on the recipe, Shiitake Mushrooms can be substituted for Oyster Mushrooms.

Nutritional Value USDA
MUSHROOMS,OYSTER,RAW
Amount Per 100g
Calories 33
%Daily Value*
 
0%
Total Fat 0g
0%
Saturated Fat 0g
Polyunsaturated Fat 0g
Monounsaturated Fat 0g
0%
Cholesterol 0mg
0%
Sodium 18mg
8%
Potassium 420mg
2%
Total Carbohydrate 6g
8%
Dietary Fiber 2g
Sugars 1g
Protein 3g
* Percent Daily Values are based on a 2,000 calorie diet. Your Daily Values may be higher or lower depending on your calorie needs.
Nutrition

We suggest that Mushrooms be cooked for two primary reasons. The first is that Mushrooms can contain small levels of toxins and carcinogens. Cooking heat breaks them down significantly. The second reason is that many of the beneficial nutrients in Mushrooms are locked away behind indigestible chitin in the Mushrooms tough cell walls. Cooking heat weakens the chitin and thus makes the Mushrooms more nutritious.

Oyster Mushrooms are rich in B Vitamins—they are an excellent source of Pantothenic Acid and a good source of Vitamin B6, Niacin, Thiamin and Folate. Additionally, they hold concentrated minerals and are an excellent source of Magnesium, Iron and Copper, a very good source of Zinc, Riboflavin, Phosphorus, and Potassium, a good source of Manganese and a variety of Phytonutrients. Their Protein content isn’t bad either at 3%.

Oyster Mushrooms are also a good source of Dietary Fiber. They are low fat, low sugar and gluten free.

On the health front, Oyster Mushrooms have been studied for antibiotic properties since the 1950’s. They are also thought to be a promising source of cancer fighting and cholesterol lowering nutrients. Oyster Mushrooms contain two molecular mechanisms (beta glucan and glycoprotein) that “specifically inhibit growth of colon cancer cells and breast cancer cells,” according to a paper in the International Journal of Oncology. The cancer fighting properties of the molecules in Oyster Mushrooms help improve the body’s natural anti-cancer responses and outperformed those in Button Mushrooms, Shiitake Mushrooms and Enoki Mushrooms.

Oyster Mushrooms are also an excellent source of natural lovastatin which, it is suggested by research, helps reduce triglycerides and LDL Cholesterol, essentially making Oyster Mushrooms a boon for those trying to lower their bad cholesterol levels.   

Relying on Oyster Mushrooms alone and avoiding or delaying conventional medical care for cancer may have serious health consequences. Use Shiitake Mushrooms as part of a balanced diet, and don’t overcook them (too much heat can damage their nutrients).

It is extremely important to always cook oyster mushrooms for good nutrition. Oyster Mushrooms contain “ostreolysin” which is a heat sensitive toxin that degrades above 140˚ F (60° C). Cooking also helps release the beneficial nutrients in Oyster Mushrooms.

Be aware that Oyster Mushrooms contain small amounts of arabitol, a sugar alcohol, which can cause upset stomachs for some people.

Gluten Free

Yes

Low Fat

Yes

Low Calorie

Yes