Testing Mushrooms: A Guide To Edible Identification

Testing mushrooms can be confusing and even dangerous, as some fungi contain hundreds of chemicals, and many poisonous mushrooms closely resemble edible ones. Distinguishing toxic from non-toxic mushroom species involves correctly identifying the mushroom and then referencing a mushroom field guide to determine if it is known to contain toxins. Chemical tests can be used to aid in determining the variety of some fungi, such as Schaeffer's test, which uses the reaction of aniline and nitric acid on the surface of the mushroom. Other tests include HPLC, GC-MS, and LC-MS, which are analytical techniques that combine chromatography with mass spectrometry to identify and quantify psilocybin and other compounds.

Testing for psilocybin (magic mushrooms)

One test that can be performed involves using Schaeffer's reagent, which combines aniline and nitric acid. When applied to the surface of the mushroom, a positive reaction is indicated by an orange to red colour, characteristic of species in the section Flavescentes. However, it is important to note that some species, such as Agaricus placomyces and Agaricus xanthodermus, can produce false-negative reactions.

Another test that can help identify magic mushrooms is the Meixner test (also known as the Wieland test). This test uses concentrated hydrochloric acid and newspaper to detect the presence of deadly amatoxins found in some mushroom species.

A more advanced method for analysing psilocybin is High-Performance Liquid Chromatography (HPLC). This technique separates the components of a sample based on their interaction with a stationary phase and a mobile phase, allowing for the identification and quantification of psilocybin and other compounds.

Additionally, Gas Chromatography-Mass Spectrometry (GC-MS) is a common technique for psilocybin analysis. It combines gas chromatography, which separates the components of a mixture, with mass spectrometry, which reveals the molecular structure of the compounds. This method provides high sensitivity and specificity in identifying and quantifying psilocybin and similar compounds.

It is important to remember that these tests may require specialised equipment and expertise, and even with accurate testing, there is always a risk of consuming mushrooms with unknown toxins or hallucinogens.

Distinguishing toxic from nontoxic mushrooms

Firstly, it is important to learn which family the fungus belongs to. For example, the edible members of the Agaric family have pink to brown/black gills, a white cap, and usually a stout stem with a skirt. However, there are toxic members of this family that look very similar. If the cap stains bright chrome yellow, it is likely poisonous; if it stains pale yellow, pink, or red, it is probably edible. Another way to distinguish Agarics is by their smell. Edible Agarics smell pleasant, sometimes with hints of aniseed or almond, whereas toxic mushrooms smell of Indian ink, iodine, or chemicals.

Another family of mushrooms is the Boletes, including the Boletus, Suillus, and Leccinum families. These mushrooms are easily identified by their sponge-like pores and generally stout stems, rather than gills. To determine edibility, two checks can be performed. Firstly, if there is any red on the mushroom, including the cap, stem, or pores, treat the mushroom as poisonous. Secondly, cut the mushroom in half vertically, and if the flesh stains blue, it is toxic.

The Lactarius family, also known as Milkcaps, exudes a milky substance from the gills when touched or damaged. This milk can be very acrid or hot, so it should not be tasted unless you are confident in your identification of Milkcaps. Most Milkcaps are toxic, so it is best to avoid any fungi that lactate from the gills.

The Russula family is another group of mushrooms, some of which are poisonous, and some of which are edible. The only way to tell if a Russula is poisonous is by performing a taste test. If the mushroom tastes hot, it is poisonous, and if it tastes mild, it is edible. However, it is important to note that taste-testing mushrooms can be dangerous, and it is not recommended unless you are certain that the mushroom is from the Russula family.

Some other ways to identify toxic mushrooms include checking the cap shape and the presence of scales or warts. Amanita mushrooms, for example, have a very wide cap that resembles an upside-down letter "U" or a parasol. Additionally, Jack o'lantern mushrooms are very toxic, and they can be distinguished by their true gills, which are forked and knife-like, and can be removed without damaging the cap. Chanterelle mushrooms, on the other hand, have false gills that break when separated from the cap, and they are safe to consume.

Chemical tests can also aid in mushroom identification. The most useful tests include Melzer's reagent and potassium hydroxide. Household ammonia can also be used by placing a few drops on the flesh of the mushroom to observe any color changes. Schaeffer's test, which uses the reaction of aniline and nitric acid on the surface of the mushroom, results in an orange-to-red color for species in the section Flavescentes.

It is important to note that picking up and looking at a poisonous mushroom will not cause any significant amount of toxins to be absorbed through the skin. Touching or handling toxic mushrooms will not make you sick; they must be ingested. However, it is always recommended to seek expert identification before consuming any wild mushroom.

Using chemical tests for mushroom identification

There are several chemical tests available for mushroom identification, which can help determine the variety of fungi and whether they are safe to eat. Some of the most useful tests include Melzer's reagent, Schaeffer's test, and the application of potassium hydroxide (KOH) and iron salts (FeSO4).

Melzer's Reagent

Melzer's reagent is a useful test for mushroom identification, though specific details of how to perform it were not readily available.

Schaeffer's Test

This test uses the reaction of aniline and nitric acid on the surface of the mushroom. Two intersecting lines are drawn on the surface of the cap, the first with aniline or aniline water, and the second with an aqueous solution of 65% nitric acid. A positive reaction, indicated by an orange to red colour, is characteristic of species in the section Flavescentes. Agaricus placomyces and Agaricus xanthodermus produce false negative reactions.

Potassium Hydroxide (KOH)

A 3–10% solution of KOH can be applied to the mushroom to observe any colour changes. For boletes, place a drop on the cap, stem, sliced flesh, and pore surface. For polypores, apply the KOH to the flesh and the cap surface. For gilled mushrooms, place a drop on the cap surface. A change to yellow is sometimes found in species of Agaricus and Amanita; magenta or olive reactions can help identify species of Russula and Lactarius; deep red or black reactions can help identify many gilled mushrooms; black reactions among polypores are crucial separators; and various colours are produced with boletes. It is important to note that a "negative" reaction (no colour change) can also be informative.

Iron Salts (FeSO4)

Iron salts are commonly used in Russula and Bolete identification. A 10% solution of iron salts dissolved in water is typically applied to the flesh of the mushroom, although sometimes the dry salts can be applied directly. Three results are expected: no change indicates a negative reaction; a colour change to olive, green, or blackish green; or a colour change to reddish-pink.

Household Ammonia

Household ammonia can also be used for mushroom identification. A couple of drops are placed on the flesh of the mushroom. For example, Boletus spadiceus gives a fleeting blue to blue-green reaction.

Additional Identification Methods

In addition to chemical tests, there are other methods to help identify mushrooms. For example, the Agaric family of mushrooms typically have pink to brown/black gills, a white cap, and a stout stem with a skirt. If the cap stains bright chrome yellow, it is likely poisonous, whereas if it stains pale yellow, pink, or red, it is probably edible. However, it is important to perform a further test to establish toxicity: smelling the mushroom. Edible Agarics smell pleasantly of mushroom, sometimes with hints of aniseed or almond, while toxic mushrooms smell chemically unpleasant, like Indian ink or iodine. Another example is the Russula family, where any hot-tasting mushrooms are poisonous and any mild-tasting ones are edible.

Testing for amanitins, the deadliest mushroom poisons

Amanitins are deadly poisons found in some species of mushrooms. Chemical tests can help identify these toxic mushrooms and prevent poisoning. One such test is the Meixner test (also known as the Wieland test), which uses concentrated hydrochloric acid and newspaper to detect the presence of amanitins. This test is crucial as consuming amanitin-containing mushrooms can lead to severe health consequences, including death.

The Meixner test is a reliable method for detecting amanitins, but it is essential to follow the procedure precisely. Here is a step-by-step guide to performing the Meixner test:

• Prepare the reagents: You will need concentrated hydrochloric acid and a small piece of newspaper.
• Apply the reagents to the mushroom: Place a few drops of concentrated hydrochloric acid on the mushroom's cap or stem. Then, place the piece of newspaper over the acid-treated area.
• Observe the reaction: Any presence of amanitins will cause a distinct colour change in the newspaper. This colour change is a positive indication of amanitin toxicity.
• Interpret the results: A positive test result indicates the presence of deadly amanitins, rendering the mushroom unsafe for consumption. It is imperative to discard the mushroom and avoid ingestion.

In addition to the Meixner test, there are other chemical tests that can aid in mushroom identification and toxicity assessment. Schaeffer's test, for example, uses the reaction between aniline and nitric acid on the mushroom's surface. A positive result is indicated by an orange to red colour, characteristic of species in the Flavescentes section.

While chemical tests are valuable tools, it is important to combine them with other identification methods, such as morphological characteristics and ecological context, to comprehensively determine a mushroom's edibility. Taste-testing mushrooms is never recommended, as it can have fatal consequences. Consulting field guides and expert sources is always advisable when in doubt about a mushroom's edibility.

Identifying Agaricus mushrooms

Identifying mushrooms can be a tricky task, and it is important to be sure before consuming any wild mushrooms. The Agaricus genus contains more than 300 species that grow all around the world. Some are edible, while others are toxic.

The most common Agaricus mushroom is the field mushroom (Agaricus campestris), which is a very good edible species. It is closely related to the supermarket button mushroom (Agaricus bisporus). Field mushrooms are widespread and common in Britain, Ireland, Europe, North Africa, Asia, and the USA. They have a truly worldwide distribution. They can be found growing in fairy rings, but more often they occur as singletons or in small groups. They have white caps, dark brown cap scales, and white gills that graduate in appearance from white, to pink, to brown as the mushroom matures. They also feature a partial veil that forms a ring on the stalk.

Agaricus arvensis, the so-called "horse mushroom", is another edible mushroom, but there are at least two distinct species that go by this name. It stains yellow.

Agaricus sylvaticus, or the pinewood mushroom, is an edible species that stains reddish when cut.

Agaricus xanthodermus is a toxic species that can be identified by its yellow staining, which fades to brown over time. It used to grow in large fairy rings.

To identify Agaricus mushrooms, it is important to consider whether the mushroom stains when bruised, cut, or handled, as well as the aroma of the mushroom. Agaricus mushrooms typically have three types of aromas: bland or indistinct, sweet (often like almonds), or foul (like library paste, phenol, or otherwise "icky chemically"). In general, sweet-smelling Agaricus species are considered good to eat, while foul-smelling ones are not. It is also possible to use a microscope to examine the basidia, as the spores are too similar to differentiate.

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