2,4,6-Trichloroanisole
2,4,6-Trichloroanisole (TCA) is a chemical compound that represents one of the strongest of off-flavors, substances "generated naturally in foods/beverages [that considerably] deteriorate the quality" of such products. 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. Chemically, TCA is a chlorinated derivative of anisole, and it is a fungal metabolite 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. The precursors can result from the reaction of hypochlorites with lignin, or can also migrate from other manufactured objects (e.g., shipping pallets treated by chlorophenols or materials stored in the presence of trichlorophenol-treated fiberboard). 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." Further reading
 
 
  An early primary research report on the role of TCA in cork taint. See also 
 2,4,6-Tribromoanisole

References

Chlorobenzenes
Phenol ethers