2,4,6-Trichloroanisole (TCA) is an organic compound with the formula CH3OC6H2Cl3. It is the symmetric isomer of trichloroanisole. It is a colorless solid.

Occurrence

2,4,6-Trichloroanisole represents one of the strongest of off-flavors, substances "generated naturally in foods/beverages [that considerably] deteriorate the quality" of such products. It is also a component of some drinking waters. It has also been detected in blood samples.

Wine

As of 2000, TCA was considered the primary chemical compound responsible for the phenomenon of cork taint in wines, and it has an unpleasant earthy, musty and moldy smell.

Coffee

TCA has also been suggested as cause of the "Rio defect" in coffees from Brazil and other parts of the world, which refers to a taste described as "medicinal, phenolic, or iodine-like". In investigation of the mechanism of its role in producing off-flavor effects, it was found to "attenuate olfactory transduction by suppressing cyclic nucleotide-gated channels, without evoking odorant responses."

Formation

TCA is formed by the methylation of 2,4,6-trichlorophenol. More generally, it may be produced when naturally occurring airborne fungi and bacteria are presented with chlorinated phenolic compounds, which they then convert into chlorinated anisole derivatives. Species implicated include those of the genera Aspergillus, Penicillium, Actinomycetes, Botrytis (e.g. Botrytis cinerea), Rhizobium, or Streptomyces. The chlorophenol precursor, 2,4,6-trichlorophenol, is used as a fungicide; more generally, related compounds can originate as contaminants found in some pesticides and wood preservatives, or as by-products of the chlorine bleaching process used to sterilize or bleach wood, paper, and other materials.