The nutritional value of mushrooms

The last decade has come with an increase in mushroom consumption due to a good content of protein, minerals and other nutritional substances. More than 2000 species exist in nature but only a number of approximately 22 species are intensely cultivated for commercial purposes. Apart from their well-known role in feeding animals and humans, they are also appreciated for their medical, nutraceutical and pharmaceutical benefits. Their use in the medical department is to be blamed on dietary fibers but mainly on chitin, a polysaccharide from the glucose family found in the exoskeleton of crustaceans and insects and beta glucans. The presence of specific bioactive compounds makes mushrooms therapeutically valuable for the immune system. They can prevent life threatening disease and work as cures for different illnesses. They are also known to exhibit antitumor, antiviral, antibacterial, hypotensive activities.

The carbohydrates in mushrooms are present in the form of monosaccharides, derivates, oligosaccharides, mannitol, trehalose. Trehalose is known for its potential to synthetize stress-responsive factors in human cells. Fungi rich in protein hold all the essential amino acids. They also have unsaturated fatty acids especially linoleic and oleic acids. Linoleic acid is famous for its anti-carcinogenic benefits on almost all stages of tumorigenesis and it reduces tumor growth by altering the 5-hydroxyeicosatetraenoic acid. It also contributes to mushroom flavor. The lipid fraction has antioxidant compounds like tocopherol. Regarding vitamins, they are rich in vitamin B complex and vitamin D. Under UV light, they produce D2 in great amounts. If we were to talk about minerals, mushrooms have proven themselves to be carriers for potassium, calcium, phosphorus and magnesium. Sodium is present in relatively small quantities making mushrooms suitable for hypertensive people’s diets. Mushrooms consumed fresh are known to lower the total cholesterol levels and support heart’s health. The presence of dietary fibers with non-dietary carbohydrates offers a wide range of health benefits.

Moreover, they are excellent functional and nutritional foods that contain selenium, ergothioneine, iron, etc. The bioavailability of any nutrient depends on the type of mushroom. They dry weight of ergothioneine varies between 0.2-2.0 mg/g. (king oyster, shiitake, oyster)

Their richness in dietary selenium contributes to their capability of reducing oxidative stress. Boletus edulis is said to have the highest concentration of selenium, 20 µg/g dry weight. Ergosterol under UV light exposure converts to vitamin D2. A study recorded the fact that UVB exposed mushrooms enhance mineralization and bone growth. Other nutrients like vitamin B12 present in fungi is quite similar to the one found in animal tissues making them perfect for a vegan’s diet. Dried mushroom powder like shiitake and oyster added in the daily diet is responsible for boosting the blood hemoglobin concentration and iron levels.

Mushroom nutraceuticals have been used since the ancient times for their medical benefits. Vitamin B is important for strengthening the nervous system, β-glucans empower the immune system and other minerals have antioxidant capacity. The polysaccharide content has well known antitumor, immunomodulatory and anti-inflammatory benefits. The antitumor activity is mediated through the thymus-dependent immune mechanism. A polysaccharide extracted from Agaricus bisporus exhibits a wonderful inhibiting action against human breast cancer. A novel heteropolysaccharide made form glucose units showed a great antitumor activity against HepG-2 cells. Proteins extracted from mushrooms are proved to have physiological activity in the gastrointestinal tract by enhancing nutrient absorption, inhibiting enzymes and modulating the immune system. Lecitins, ribonucleases and laccases have pharmaceutical attributes. Specific compounds also target free radical activity inhibiting the appearance of oxidative stress. Ganoderma lucidum, a mushroom used worldwide in therapy has more than 500 bioactive molecules like flavonoids, terpenoids, peptides and others. They are anti-diabetic, antioxidant, a free radical scavenger.

Researchers state that cooking methods used on mushrooms do not necessarily alter their nutritional benefits.

Due to the variety, availability and many cultivation methods, mushrooms emerge as the next generation’s source of nutritional food. They are considered to be a complete food suitable for the population thanks to their large amount of proteins, dietary fibers, vitamins and mineral contents. Along with their nutritional benefits they stand as strong candidates in the medical field and pharmaceutical industry. So, it’s fair to say that mushrooms should be taken into account by every researcher with the purpose of exploiting their many positive roles.

A report by Malina Puia

  1. Rathore, S. Prasad, S. Sharma, “Mushroom nutraceuticals for improved nutrition and better humanhealth: A review”, 2017
  2. Sharif, et al., “Wild Mushrooms: A Potential Source of Nutritional andAntioxidant Attributes with Acceptable Toxicity”, 2017
  3. Manzi,” Nutritional values of mushrooms widely consumed in Italy”, 2000
  4. A. Murugkar and G. Subbulakshmi, “Nutritional value of edible wild mushrooms collected from theKhasi hills of Meghalaya”, 2004
  5. J. Feeney, et al., “MushroomsVBiologically Distinct andNutritionally Unique”, 2014

Wild Oyster Mushrooms & Sweet Potatoes

     

After two days of slow rain I’ve decided to visit the woods nearby -a deciduous forest not quite at it’s climax but I’ve seen there goodies before. I took my horse and rode it but stopped to charge my batteries with some good old beer -it helps with identification. After a two hour walk I couldn’t find anything but bloody moskitoes. Then, suddenly my face turned pink when I saw at a distance a fallen log packed with oyster mushrooms (it was May -around 70 F outside). Oyster mushroom is quite easy to recognize in the field: mid to large funnel shaped caps, white to colored (with darker patches, brownish, or gray); white-cream gills underneath; thick somewhat woody stalks with decurrent gills; white flesh, mild taste, and pleasant odor. Half of them were kinda old so I collected the other fresh half and left with a smile on my face. Oh! gee, one more find: an old porcini was laying on the ground next to my feet -it was loaded with shlimax so I just left it were it was. 

There are times when you need to be pleased with what you find, so on my mind was how to turn my find into something delicious. There are so many ways on how to prepare oyster mushrooms but I’ve decided to go for something simple, just to feel the mushroomy flavor. I’m the adept of a healthy diet but some flavors need some sacrifice. I will tell you what! we’re extreamly addicted to the taste that we’re used to, I mean, you name it: steak, pizza, burgers, any good food that you can think of. Unfortunately, we would even die for it. Think about lots of people out there suffering from random illnesses, deep in their minds they know that this or that is bad for them and they still eat that crap. So back to the recipe, I used a carefully cut slice of pork fat which turned the whole thing slightly smoky.

Ingredients:

  1. A good slice of smoky pork fat (go for organic)
  2. Green onion -lots of it (3-5 will make it)
  3. Cherry tomatoes (5-10 pc.)
  4. Thin sliced oyster mushrooms (1-2 lbs)
  5. Salt & pepper
  6. Sweet potatoes (4-6 pc.)
  7. Parsley (a pinch)

If you add 2 eggs to it will be even better. You may switch the pork fat for butter which will provide this recipe a mild and smooth flavor. You may also substitute the tomatoes for some tomato sauce. 

Procedure:

Take a pan heat it up on the fire and place the pork fat slice in there, leave it for 1-2 minutes to melt, then add the chopped onions and let them get color. Next add the sliced oyster mushrooms and the cherry tomatoes. Apply salt and pepper on top and place a lid on top. Let it simmer for 10-15 minutes. Take a pot and boil the sweet potatoes in it (15-20 mins will suffice). Next place the food on a dish and spread some parsley or some basil on top.

Wild oyster mushrooms (Pleurotus sp.)
Sweet oyster blend!

This combination with sweet potato is wonderful but if you don’t like sweet potatoes regular ones will be just fine. What i like about this recipe is that is quick, simple, easy to make, and delicious. Try it and hit me up with some better versions of it.

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Wild Mushrooms: Identification Advice

Make sure to use several identification guides just because some might have incomplete descriptions of some important characters used in the identification process.  Also make sure that these guides have pictures of the mushroom species discussed. Another important aspect is the description itself which could be in depth describing both macro-morphological and micro-scopical features.

Use guides that describe fruitbody macro-morphology for easy to identify mushrooms. Use complete guides [with both macro and micro-morphology description] for species that seem to be hard to identify.

Don’t rely on pictures too much: Especially fleshy mushrooms found in different development stages show different colors or characteristics. Colors in fleshy mushrooms might change according to environmental conditions such as humidity or temperature. Therefore this is a less reliable feature.

Pictures sent via internet won’t give you accurate identifications results unless the mushroom to identify is an ‘easy one’ for an expert.  In some other cases one picture of a mushroom sent via internet with a request for identification is non-sense since there are so many features that overlap case in which not even experts won’t be able to tell you what it is. Besides one picture is just ‘one side of the moon’ in most cases doesn’t show all the characteristics that you need in order to identify that mushroom.

For in depth analyses you’ll need a microscope. In this case spore shape, size, ornamentation or color is important to analyze along with presence of clamps or septa on the hyphae.

What to look for when you want to identify mushrooms?

Habitat –is quite important since some mushroom species are more likely to appear in some types of forests than in others. Some species prefer conifers while some others prefer hardwoods or both. Some other mushrooms prefer grassland. Some species are commonly found in all types of habitats both in boreal and subtropical or tropical climate types –these are particularly well adapted fungi species to various substrates or climatic conditions.

Frequency -if the mushrooms is commonly found or not. Some mushrooms are rather rare but when you’ll find them they will be all over while some other are common but can be hardly found one next to each other.

Season – This is important because this way you can exclude some species that are considered poisonous ‘look alikes’ that may pop up in a different season.

General aspect –single fruitbodies/clusters/mushroom fruitbody outline.

Cap surface –color/scale presence/shape/margin.

Under-cap –gills/pores/teeth/ or combinations? Color?

Stem –shape/color/ring presence or absence/stem base color/rhizomorphs ..

Flesh –consistency or oxidizing reaction in presence of air are just two of the important characters that one needs to look for.

Spore print –in some species has an important role in the mushroom ID especially in those that present poisonous look-alikes that present a different spore print color.

Odor –is an important character because in some species of fungi have specific odors that tells us if they are poisonous or not.

Possible changes –refer to the ontogenetic development of a mushroom fruitbody or environmental changes that affect cap color or size.

All these features are differently evaluated by various authors –that’s why you need to use several guides when trying to get a mushroom ID. Some authors simply might overlook some important features. Reading several descriptions will get you a general description that includes lots of important characters.

 

Other important things to consider..

An expert advice always matters

Inform yourself and study the poisonous mushrooms from your area or areas that you would collect from. Check for mycological societies around –usually they have checklists comprising the mushroom species found in the collection area.

Don’t pick up mushrooms that ‘ you believe’ that you know them. Being 90% sure of the ID of that mushroom is not what you want especially if you think to fry that mushroom.

Don’t pick up edible mushrooms when you found them near poisonous ones.

If you focus on 5 edible mushrooms that you know very well that narrows the risk of poisoning.

If your 5 species are hard to confuse with poisonous mushrooms that’s even better. Make sure that none of them belong to the Amanita family.

Several opinions on a mushroom ID matters.

Always heat treat your mushroom crop before eating them.

 

DNA identifications

We cannot rely only on DNA analyses in order to identify fungi and this because of several reasons such as:

  1. Lack of sequences available in databases like Genbank for some fungi species [especially rare fungi]
  2. Poor sequence availability for some other fungi
  3. Single publications listing several sequences for the same species. Usually for a more accurate identification you need to consider and compare sequences resulted from multiple authors.
  4. Sequences resulted from basidiocarps collected in different geographical regions of the world might show a bit of genetic shift.
  5. We should take into consideration DNA sequences resulted from the analyses of several genes and not only one.
  6. Some DNA sequences resulted from some genes are more reliable than others [compare D2 to ITS4].
  7. In some cases you cannot rely on DNA sequences just because they can be easily modified and adapted according to the desire of the person working with them.
  8. Sometimes researchers cannot get a complete sequence of a gene.

According to my opinion we should always try to identify fungi according to classical mycology methods [macro and micro-morphological aspect] –this works pretty much for most fungi [it is also less expensive than DNA isolation]. However, some fungi species require additional analyses such as morphological aspect of colonies in pure culture [e.g., Phellinus baumii and Ph. Linteus –in which you won’t see differences in fruitbody morphology but they are different when grow on solid media]. For some rather hard to identify fungi I would recommend data collection from classical morphological analyses and DNA.

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