Chemical tests in mushroom identification
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Chemical tests in mushroom identification are methods that aid in determining the variety of some fungi. The most useful tests are Melzer's reagent and potassium hydroxide.
Contents
Ammonia
Household ammonia can be used. A couple of drops are placed on the flesh. For example, Boletus spadiceus gives a fleeting blue to blue-green reaction.
Iron salts
Iron salts are used commonly in Russula and Bolete identification. It is best to dissolve the salts in water (typically a 10% solution) and then apply to the flesh, but it is sometimes possible to apply the dry salts directly to see a color change. For example, the white flesh of Boletus chrysenteron stains lemon-yellow or olive. Three results are expected with the iron salts tests: no change indicates a negative reaction; a color change to olive, green or blackish green; or a color change to reddish-pink.[1]
Meixner test for amatoxins
The Meixner test (also known as the Wieland test) uses concentrated hydrochloric acid and newspaper to test for the deadly amatoxins found in some species of Amanita, Lepiota, and Galerina. The test yields false positives for some compounds, such as psilocin.[2]
Melzer's reagent
Melzer's reagent can be used to test whether spores are amyloid, nonamyloid, or dextrinoid.
- Spores that stain bluish-gray to bluish-black are amyloid
- Spores that stain brown to reddish-brown are dextrinoid
This test is normally performed on white spored mushrooms. If the spores are not light colored, a change will not be readily apparent. It is easiest to see the color change under a microscope, but it is possible to see it with the naked eye with a good spore print.
Paradimethylaminobenzaldehyde
In the genus Lyophyllum the lamellae usually turn blue with the application of para-Dimethylaminobenzaldehyde (PDAB or pDAB).
Phenol
A 2–3% aqueous solution of phenol gives a color change in some species when applied to the cap or stem.
Potassium hydroxide
A 3–10% solution of potassium hydroxide (KOH) gives a color change in some species:
- In Agaricus, some species turn yellow with KOH, some have no reaction, and one species turns green.
- Distinctive change for some species of Cortinarius and Boletes
Schaeffer reaction
Developed by Julius Schäffer to help with the identification of Agaricus species. A positive reaction of Schaeffer's test, which uses the reaction of aniline and nitric acid on the surface of the mushroom, is indicated by an orange to red color; it is characteristic of species in the section Flavescentes. The compounds responsible for the reaction were named schaefferal A and B to honor Schäffer.[3]
Two intersecting lines are drawn on the surface of the cap, the first with aniline or aniline water, the second with an aqueous solution of 65% nitric acid. The test is considered positive when a bright orange color forms where the lines cross.[4][5][6]
Agaricus placomyces and Agaricus xanthodermus produce false negative reactions.[4][5]
Sometimes referred to as "Schaeffer's reaction", "Schaeffer's cross reaction" or "Schaeffer's test".
Sulfo-vanillin
Made from sulfuric acid (H2SO4) and vanillin (vanilla). Used in Russula and Panaeolus identification.
References
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- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- Arora, David "Mushrooms Demystified" 2nd Edition, Ten Speed Press, Berkeley, 1986
- Jordan, Michael "The Encyclopedia of Fungi of Britain and Europe" Frances Lincoln 2004
- Kuo, Michael "100 Edible Mushrooms", University of Michigan Press, Ann Arbor 2007
- Largent, David L., Baroni, Timothy J. "How to Identify Mushrooms to Genus VI: Modern Genera" Mad River Press 1988
