Oyster mushrooms: properties, health benefits and cooking ideas

Despite the fact that there are at least 150,000 species of mushrooms on the face of the earth (in fact, it is estimated that there are around 5 million species) with the most varied but always surprising characteristics [1], only 60 are cultivated commercially and barely 10 of these magnificent fruits are produced globally on a large scale [2]. It is therefore not at all acceptable that when we say mushroom, we unquestionably mean button mushrooms.

Oyster mushrooms, although they cannot compete in popularity with Agaricus Bisporus (the button mushrooms: they make up 40% of the mushrooms cultivated worldwide [3]), are nevertheless part of the elite, of the most cultivated mushrooms.
In Italy they are also known as orecchioni (big ears), due to their shape similar to a large ear; but globally they are called oyster mushrooms, thanks to their scientific name Pleurotus ostreatus, derived from their similarity to the oyster.
Pleurotus mushrooms are among the fleshiest and tastiest cultivated mushrooms; however, as you know by now, taste is never the only reason I want to talk about a particular food: the good oyster mushroom seems to have been created especially for those who care about the future of the planet, or who are sensitive to ‘waste’, as well as those who want to reduce or eliminate meat from their diet.

Nutritional values and properties of Pleurotus ostreatus mushrooms

– According to the U.S. Department of Agriculture’s Food Data Central, ingesting 100g of mumps yields approx:

3.3g of protein, 0.4g of fat, 2.3g of dietary fibre and 6g of carbohydrates, for a total of 33kcal.

– the protein profile is made up of all the essential amino acids and is of good biological value[4]; due to its protein digestibility it is placed between foods of vegetable origin with higher bioavailability and those of animal origin with lower bioavailability[5];

– the carbohydrates present do not contain starches, and consist of 2g of dietary fibre and 1g of sugars

– they also contain a good quantity of minerals (particularly potassium, selenium, iron, zinc and phosphorous) and vitamins (niacin (B3), pantothenic acid (B5), folic acid (B9) and choline (also known as vitamin J));

– like all mushrooms, pleurotus mushrooms are also a good source of pro-vitamin D (0.7µg in 100g);

Extra tip

Vitamin D deficiency is a plague that negatively affects the health of the world’s population (for more information read here).
Non-animal sources of vitamin D are crucial to the supply of people who cannot (for economic, health or religious reasons) or do not want to (for ethical reasons) include animal products in their diets. Mushrooms can therefore be a great help in meeting daily requirements, as they are one of the few non-animal foods that can synthesis vitamin D by converting ergosterol into vitamin D2 in the presence of sunlight.
Here’s what you should do to further increase the levels of Vit D2 in oyster mushrooms: sunbathe them after cutting them into approximately 2 cm slices.
According to a study carried out in 2018, exposure to direct sunlight for less than 30 minutes exponentially increases the D2 content, without losing any other nutrients and organoleptic qualities [6].
In another study carried out in Germany during the summer, mushroom slices placed in the sun at midday had approximately 17.5μg/100g FW (Formula Weight) of Vit D2 after 15 minutes; after 60 minutes in the sun, they contained 32.5μg/100g FW [7].
To be fair, there are also other studies which, although confirming a tangible increase, emphasis the low bioavailability of Vitamin D2, not detecting any increase in the serum and calling for more research to investigate this issue in depth [8].
In any case, since it is a non-harmful process and does not require any effort, I always expose my mushrooms to the sun first whenever I cook them. It would be neither the first nor the last time that the human body would act in ways that are now mysterious, thus catching the researchers of the second school of thought off guard!

– contain special substances such as phenolides with antioxidant properties, which can stimulate the body’s own antioxidant mechanism (just like curcumin) as well as fighting free radicals on the front line;

– in the antioxidant field, we still have two molecules of extraordinary quality: glutathione and ergothioneine, considered to be effective soldiers against free radicals. In addition to being considered one of the best antioxidants, glutathione plays a key role in immune defense.

Ergothioneine, on the other hand, is particularly specialized against aging, not only of the body but also of the brain, and you will be pleased to know that the entire Pleurotus species is rich in it and is selected for the extraction of this new ‘vitamin’ [9, 10];

– the delicious oyster mushroom is also rich in beta-glucans, i.e. just like oats, it is able to reduce cholesterol levels and other inflammations: the quantity of this extraordinary molecule is double that of mushrooms [11].

Not bad at all, considering the economic outlay of just 50-60 euro cents per 100g, sometimes even less.
 

But what does it taste like?

Not to worry, although it has several therapeutic characteristics, the taste is not as unpleasant as you would expect from a ‘medicine’, on the contrary; it is one of my favorites among cultivated mushrooms and it is not just a matter of personal preference.
It is well known that all mushrooms are rich in umami (the fifth taste, which is complicated to explain, but when you taste two foods, one with a little and the other with a lot of umami, you can identify without any doubt which has it and which does not); Pleurotus ostreatus, according to tests carried out on humans, is the richest in this particularity compared to other mushrooms [12].
Again, we find them in this dual function: very useful for enriching meatless meals with flavor, and very important functional molecules.

I had mentioned their exceptional nature: as well as being delicious, healthy and cheap, they are also environmentally friendly.

How can pleurotus mushrooms be environmentalists?

Mushrooms belong to a world of their own, which differentiates them from both the plant and animal kingdoms; although they do share some distinctive characteristics.
First of all, you don’t need soil or feed to grow them; mushrooms become delicious, nutritious and, as we have seen, incredibly functional by recycling lignocellulosic waste from agricultural and forestry activities (such as bagasse and sugar cane, straw, maize, bushes, grass or residues from pruning, sawmills and the like).
These wastes are easily accessible and abundantly available; moreover, their natural decomposition could cause health risks and environmental pollution: therefore they must be treated for disposal, with costs that can be significant.
In this case, mushrooms are providential twice over: firstly in recycling, or rather giving a second life to a precious and underused raw material, avoiding waste; then in eliminating the energy and resources needed for its disposal.
But it doesn’t end there, mushroom cultivation is really full of solutions typical of a circular economy: this biomass used as if it were soil (in the sector it is called substrate) after being used for mushroom cultivation, could be further recycled in order to cultivate other mushroom species, or to enrich livestock feed, or even as an organic additive and fertilizer, and in environmental remediation [13].
Nevertheless, the production of mushrooms is also energy-dependent.
Energy is particularly needed for:

– pasteurize substrates to avoid contamination;

– heating, lighting and cooling the environment when required;

– circulating air to maintain the delicate balance of CO2 and O2 and,

– maintain humidity in precise ranges.

In a scientific study carried out to derive the actual energy cost of mushroom cultivation, it was found that 0.22kWh was needed to produce 1kg of product [14]; considering that to produce 1kg of steak from grain-fed (non-grazing) beef requires more than 15,000l of water, 10kg of grain, 70kg of topsoil and the energy equivalent of 8 litres of gasoline [15] I would say that we can be more than satisfied.
In addition, the experiments within the EU Horizon 2020 Framework Program project – “Smartmushroom”, foresee their transfer to a large scale: they are integrated mushroom cultivation systems with adjoining biogas production, so as to be 100% energy-independent and zero-waste; in the pilot plant, the production of organic fertilizers is also foreseen, thanks to the biogas generated by the substrates used.
 

How to prepare and cook them

If I have been able to convince you to give oyster mushrooms more space in the kitchen, here are some ways to cook them:

– grilled/baked (my favorite way)

– in the pan

– as a pizza topping

– to use as fillings in your meatless patties

– to prepare meatless meatballs

Directions

Before washing the oyster mushrooms quickly under running water, remove the bases in case they contain any substrate residue.
Then pat dry with a tea towel.
The ends of the stems can sometimes be very hard and woody, but you don’t need to remove them; just chop them finely and add them to other more edible parts.
If you want to cook them in the oven or on the grill, I suggest leaving them to marinate for half an hour with the flavorings you prefer: I use garlic, black pepper, thyme and plenty of olive oil.
Put them in the oven at about 220 degrees for about 15-20 minutes: you’ll taste how good they are!
If, on the other hand, you want to enjoy them sautéed, I recommend using a very hot pan, stirring often so as not to burn them.
When they take on a pleasantly brown color, after about 7-10 minutes, you can add garlic, salt, parsley or oregano to taste.
500 g of mushrooms are enough for 2 people as a main dish to be served with a side dish; otherwise you can cook them in larger quantities at once and store them in the fridge to eat in the next few days.
Or freeze them: I have to say that I don’t like the texture of thawed mushrooms very much, but there are no contraindications in terms of health, so if you can’t eat them in time, freeze them.

Living forever is not possible, but living well very often depends on us and what we eat.

Have a good life and a good revolution

Bibliography
1) Bhatti MA, Mir FA, Siddiq M (1987) Effect of different bedding materials on relative yield of oyster mushroom in the successive flushes. Pak J Agrc Res 8:256–259
2) Wasser, S. P. (2010). Medicinal mushroom science: History, current status, future trends, and unsolved problems. International Journal of Medicinal Mushrooms, 12(1), 1–16.
3) AS Sonnenberg, JJ Baars, W Gao, RG Visser (2017). Developments in breeding of Agaricus bisporus var. bisporus: progress made and technical and legal hurdles to take. Appl. Microbiol. Biot, 101: 1819-29.
4) P. Kalac (2013). A review of chemical composition and nutritional value of wild-growing and cultivated mushrooms. Journal of Science and Food Agriculture, 93, 209-218
5) Zakia Bano, S. Rajarathnam & Keith H. Steinkraus (1988) Pleurotus mushrooms. Part II. Chemical composition, nutritional value, post‐harvest physiology, preservation, and role as human food, Critical Reviews in Food Science and Nutrition, 27:2, 87-158
6) Keflie TS, Nölle N, Lambert C, Nohr D, Biesalski HK. Impact of the natural resource of UVB on the content of vitamin D2 in oyster mushroom (Pleurotus ostreatus) under subtropical settings. Saudi J Biol Sci. 2019;26(7):1724-1730. doi:10.1016/j.sjbs.2018.07.014
7) Cardwell, Glenn et al. “A Review of Mushrooms as a Potential Source of Dietary Vitamin D.” Nutrients vol. 10,10 1498. 13 Oct. 2018, doi:10.3390/nu10101498
8) Leung MF, Cheung PCK. Vitamins D and D2 in Cultivated Mushrooms under Ultraviolet Irradiation and Their Bioavailability in Humans: A Mini-Review. Int J Med Mushrooms. 2021;23(11):1-15.
9) Chen, S.-Y.; Ho, K.-J.; Hsieh, Y.-J.; Wang, L.-T.; Mau, J.-L. Contents of Lovastatin, γ-Aminobutyric Acid and Ergothioneine in Mushroom Fruiting Bodies and Mycelia. LWT 2012, 47, 274–278
10) Borodina, I., Kenny, L., McCarthy, C., Paramasivan, K., Pretorius, E., Roberts, T., . . . Kell, D. (2020). The biology of ergothioneine, an antioxidant nutraceutical. Nutrition Research Reviews, 33(2), 190-217.
11) Miriam Sari, Alexander Prange, Jan I. Lelley, Reinhard Hambitzer (2017). Screening of beta-glucan contents in commercially cultivated and wild growing mushrooms. Food Chemistry, 216: 45-51.
12) Phat C, Moon B, Lee C. Evaluation of umami taste in mushroom extracts by chemical analysis, sensory evaluation, and an electronic tongue system. Food Chem. 2016;192:1068-1077. doi:10.1016/j.foodchem.2015.07.113
13) Chang, S., & Wasser, S. The Cultivation and Environmental Impact of Mushrooms. Oxford Research Encyclopedia of Environmental Science. Retrieved 4 May. 2022
14) Beghi, R., Giovenzana, V., Tugnolo, A., Pessina, D. and Guidetti, R. (2020) “Evaluation of energy requirements of an industrial scale plant for the cultivation of white button mushroom”, Journal of Agricultural Engineering, 51(2), pp. 57–63.
15) Earth Save Organization web page Food Choices and the Planet

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