Dextrinoid reaction: Th is is a red to red-brown
reaction with Melzer’s reagent.
Blackwell et al (2001) suggested that the red
reaction does not involve starch or amylose, but
is a reaction with glycine betaine, an “osmolyte”
(an organic osmotic solute) which they found in
high concentrations in the Basidiomycetes they
studied. Betaine functions to attract water to
the rapidly enlarging and diff erentiating basidiomata.
Th e addition of iodine presumably results
in a “glycine betaine-IKI complex.” Baral (1987;
personal communication, 2004) noted that the
dextrinoid reaction is “strongly enhanced” by
chloral hydrate.