Oyster Mushroom guide

Oyster Mushroom guide

Guide to to the Oyster Mushroom
At BeefyGreen, we are passionate about mushrooms. From our specialized mushroom farming and harvesting, to wild mushrooms, to recipes and processing techniques, we love everything about these amazing plants, and want to share them with the world. This guide to oyster mushrooms will show what an extraordinary resource they represent, and explain why we believe they represent the future of food.

What is an Oyster Mushroom?
Oyster mushrooms or Oesterzwam (Pleurotus ostreatus), also known as pearl mushrooms, tree oysters, are recognized for their resemblance to oysters. The smooth caps have a creamy color and firm texture that gives the mushroom its common name.

Oyster Mushroom History and Cultivation
The oyster mushroom grows in temperate and deciduous forests around the world, except for the Pacific Northwest of North America, living on the wood of decomposing deciduous trees. Because it is so often found on the trunks of dead and decaying trees, particularly beech trees, some early biologists believed it to be a parasite. However, it is in fact a saprophytic organism, living on the bacteria and nematodes that thrive in decaying wood, growing on trees that are dying from other causes.
Oyster mushrooms were first documented in 1775, by Dutch naturalist Nikolaus Joseph Freiherr von Jacquin. They were first cultivated as a food source in Germany during WWI, and developed into a commercial food product in the early 1940s in response to war-time food shortages.
Since the 1940s, commercial cultivation of the oyster mushroom has spread around the world. In East Asian cuisines, it is considered a delicacy, and in parts of Asia and Europe it is prepared and served much like meat in traditional dishes.

Oyster Mushroom Anatomy

Like most edible mushrooms, the oyster mushroom consists of three primary parts: 

 

The cap. The oyster-shaped top of the mushroom, also often called the “mushroom hat, hoed, kap, blad,” etc.

 

The gills. The papery gills, also known as lamella or lamellen, are the gill-like ribs beneath the cap that are important for spore dispersal and species identification.

 

 

The stem. The stem, also called a stipe, stalk, chog, leg, food, voetje, kontje, steeltje, or pootje, supports the cap.

 

The flesh of an oyster mushroom is known for being firm, with a delicate, lightly sweet flavor that can resemble the taste of oysters, or have a hint of anise flavor.

Oyster Mushroom Properties

Oyster mushrooms are an excellent source of protein and nutrients, but they also have some unique health benefits. Mushrooms in general form a powerful class of functional foods with nutraceutical properties (source: https://www.ncbi.nlm.nih.gov/pubmed/9110582), but oyster mushrooms specifically have been shown to:

  • Lower cholesterol.  Multiple studies (source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3749453/ ) have shown that oyster mushrooms reduce LDL cholesterol and triglycerides in humans and rats.
  • Reduce inflammation. Oyster mushrooms have been proven (source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3120742/ and http://gjournals.org/GJBS/Publication/2016/June/HTML/051816091%20Zitte%20et%20al.htm) to reduce inflammation. 
  • Regulate blood sugar. Oyster mushrooms naturally contain a compound called guanide, commonly found in anti-diabetic medications. Early studies showed that oyster mushrooms improve blood sugar in normal and diabetic mice (source: https://www.ncbi.nlm.nih.gov/pubmed/22867521), but they have similar effects in humans as well.  In a randomized hospital study (source: https://www.ncbi.nlm.nih.gov/pubmed/17344789), oyster mushrooms were shown to lower cholesterol and blood pressure, and help to control blood glucose in diabetic patients.
  • Improve the immune system. Oyster mushrooms contain compounds that help to improve the immune system, and are particularly valuable for patients with compromised immune systems (source: https://pdfs.semanticscholar.org/ca80/f28914bf4cc3627e5e66430c76476dc0ee84.pdf and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5937616/). Oyster mushrooms also have anti-microbial and anti-viral compounds that are drawing increasing medical attention (source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1193547/)
  • Reduce bodyweight and obesity. In one study (source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3749453/), not only did oyster mushrooms reduce cholesterol levels in rats with high cholesterol, but the mushroom also reduced body fat in these rats by 17-24%. This aspect of the oyster mushroom has been little studied in humans, but is an often-cited benefit of adding them to your diet. 
  • Potentially fight cancer cells. Oyster mushrooms have been used medically cancer treatment for centuries. They are of natural benefit to immune-compromised patients in general, and are a healthy food rich in antioxidants and beneficial compounds. However, recent studies (source: https://www.ncbi.nlm.nih.gov/pubmed/15726350) have demonstrated that there is a scientific basis for these ancient treatments, as oyster mushrooms seem to inhibit the growth of cancer cells in prostate (source: https://www.ncbi.nlm.nih.gov/pubmed/16822205), colon, and breast cancers (source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2796484/)
    What is particularly exciting about this research is that oyster mushrooms have all these health and medical benefits, from an all-natural source, with virtually no side effects.

Oyster Mushroom Nutrition
There are numerous studies (source: https://pdfs.semanticscholar.org/32a7/81ca389e0ae6f95cc8efa92607070beadc82.pdf and https://www.degruyter.com/downloadpdf/j/fhort.2018.30.issue-2/fhort-2018-0012/fhort-2018-0012.pdf and https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/pleurotus-ostreatus) that offer deeper exploration into the unique bioactive and nutritional compounds of oyster mushrooms. While the actual nutrient levels of specific servings vary due to natural variations in season, growth, and preparation methods, here is an overview of the nutrients in oyster mushrooms, based specifically on this study: https://www.researchgate.net/publication/315992921_Nutritional_Composition_of_Oyster_Mushroom_Pleurotus_ostreatus_Grown_on_Softwood_Daniella_oliveri_Sawdust_and_Hardwood_Anogeissus_leiocarpus_Sawdust).

Macronutrients

  • 48% carbohydrates with 3% total sugars
  • 27% crude protein
  • 1% crude fat 
  • 11% crude fibre
  • 10% total ash
  • Overall protein digestibility is 79%.

Micronutrients
Mineral content per 100g dry weight (source: https://www.nutritionvalue.org/Mushrooms%2C_raw%2C_oyster_nutritional_value.html):

  • Iron: 1.33 mg
  • Zinc: .77 mg
  • Phosphorus: 120 mg
  • Manganese: .133 mg
  • Calcium: 3 mg
  • Potassium: 420 mg
  • Magnesium: 18 mg

Oyster mushrooms are also an excellent source of selenium, but selenium levels depend a great deal on the growth method and substrate of the mushroom. Several studies have been undertaken to boost selenium levels in oyster mushrooms.
Oyster mushrooms are also very high in vitamin B1, vitamin B2, vitamin B6, vitamin C, vitamin D, thiamin, riboflavin, and niacin.
What all this means is that oyster mushrooms are naturally a great source of: 

  • Antioxidants: While most edible mushrooms have high levels of antioxidants, the Pleurotus family, and oyster mushrooms specifically, are higher in antioxidants than other mushroom species (source: https://www.ncbi.nlm.nih.gov/pubmed/31666837). Antioxidants are essential for fighting damage at the cellular level, and are important for boosting physical health, as well as preserving youthful skin. 
  • Polysaccharides: Polysaccharides are special forms of fiber that affect how other nutrients are absorbed by the body. The high levels of polysaccharides in oyster mushrooms help to regulate blood sugar, lower cholesterol, and help to create short-chain fatty acids that are essential for digestive health. 
  • Peptides and lectins: Peptides and lectins are special proteins. The peptides in oyster mushrooms have beneficial anti-microbial properties, while lectins defend against invading microorganisms. These compounds are believed to be why oyster mushrooms are beneficial to the immune system. 
  • Lovastatin: Statins are the name of a group of chemicals that inhibit the metabolism of cholesterol. Oyster mushrooms have up to 216 mg/kg of lovastatins, which is why they are helpful for regulating cholesterol and improving liver and kidney function. 
  • Ergosterol: Ergosterol is a precursor to vitamin D production, so it both boosts edible vitamin D in a mushroom, and helps a human naturally synthesize vitamin D from sunlight. 
  • Fatty acid esters: The fatty acid esters in oyster mushrooms have anti-bacterial properties, and are used by the body to make healthy dietary fats.

Oyster Mushroom Uses
Oyster mushrooms are delicious and nutritious, so their use as a food source is obvious. But there are a few special reasons why oyster mushrooms are increasingly important, and why they are drawing more and more attention from food producers and food scientists.

Complete nutrition…
As stated above, actual nutrient levels in oyster mushrooms vary depending on how they are grown, but, broadly speaking, they are an excellent source of highly bioavailable protein. They are rich in vitamins C, D, and B-complex vitamins. They have most of the mineral salts a human requires for survival, and are high in fiber and alkaline ash. They boost cellular health and immunity, regulate blood sugar, improve cholesterol, and have a host of other benefits. They are safe and healthy for people with a wide range of health concerns, and they are completely natural and vegan.

…with low input
Oyster mushrooms are one of the easiest edible mushrooms to grow. They don’t require specialized habitats, compost, or manure for nutrition. They can be grown on fresh agricultural waste, such as straw, hay, wood, leaf waste, and other materials that would otherwise not be useful or provide agricultural value.
This means that oyster mushrooms are a food crop that actually benefits the environment.
Animal protein requires an average of 25 kcals of fossil fuel consumed for every kcal of energy produced, and it takes an amazing 15,000 liters of water to produce 1 kg of beef protein. On average, it takes only about 112 liters of water to produce 1 kg of protein from oyster mushrooms. Mushroom production requires little energy and does not produce methane, so it’s an excellent way to eat healthy and delicious food that doesn’t harm our natural world. 

At BeefyGreen, we think that oyster mushrooms are delicious and nutritious, and are excited to be part of the future of food. We grow oyster mushrooms that are prized for their firm, meaty texture and juicy mouthfeel, so our mushrooms can be used as either a meat additive, or a meat alternative, without sacrificing the flavour people love in their favorite dishes. We think that once you’ve tried our oyster mushrooms, you will love them too.