Chemical tests in mushroom identification

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.

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 poisonous amatoxins found in some species of Amanita, Lepiota, and Galerina.

Psilocin gives a positive Meixner test (100% false positive),^[2] therefore the Meixner test cannot differentiate between a hallucinogenic species and a deadly poisonous one.

Melzer's reagent

Melzer's Reagent can be used to test spores for amyloid, nonamyloid, and 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.

Paradiaminobenzaldehyde

In the genus Lyophyllum the lamellae usually turn blue with the application of paradiaminobenzaldehyde (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's test

Uses aniline and nitric acid on Agaricus.

Sulfo-vanillin

Made from sulfuric acid (H₂SO₄) and vanillin (vanilla). Used in Russula identification.

References

1. ^ Ammirati J, Traquair JA, Horgen PA. (1985). Poisonous Mushrooms of Canada. Fitzhenry & Whiteside in cooperation with Agriculture Canada. p. 40. ISBN 978-0889029774. 
2. ^ "The Meixner test in the detection of alpha-amanitin and false-positive reactions caused by psilocin and 5-substituted tryptamines." Beuhler M, Lee DC, Gerkin R. - Ann Emerg Med. 2004 Aug;44(2):114-20. - PMID: 15278082

• 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

External links

• MushroomExpert.com