Chemistry:2,4,6-Trichloroanisole

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2,4,6-Trichloroanisole (TCA) is an organic compound with the formula CH
3OC
6H
2Cl
3. It is one of several isomers 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.[1][2] It is also a component of some drinking waters.[3] It has also been detected in blood samples.[4]

Wine

As of 2000, TCA was considered the primary chemical compound responsible for the phenomenon of cork taint in wines,[5][1] and it has an unpleasant earthy, musty and moldy smell.[2]

Coffee

TCA has also been suggested as cause of the "Rio defect" in coffees from Brazil and other parts of the world,[6] which refers to a taste described as "medicinal, phenolic, or iodine-like".[7] 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."[1]

Formation

TCA is formed by the methylation of 2,4,6-trichlorophenol.[8][7] 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.[9] Species implicated include those of the genera Aspergillus, Penicillium, Actinomycetes, Botrytis (e.g. Botrytis cinerea), Rhizobium, or Streptomyces.[10][11][9]

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.[12]

Further reading

See also

References

  1. ↑ 1.0 1.1 1.2 Takeuchi, Hiroko; Kato, Hiroyuki & Kurahashi, Takashi (2013-09-16). "2,4,6-Trichloroanisole is a Potent Suppressor of Olfactory Signal Transduction". Proceedings of the National Academy of Sciences 110 (40): 16235–16240. doi:10.1073/pnas.1300764110. ISSN 1091-6490. PMID 24043819. Bibcode: 2013PNAS..11016235T. [non-primary source needed]
  2. ↑ 2.0 2.1 Jackson, Ron S. (2009). "Chapter 3: Olfactory Sensations" (in En). Wine tasting: a professional handbook. Food science and technology international series (2nd ed.). Academic Press. ISBN 978-0-12-374181-3. 
  3. ↑ Young, W.F.; Horth, H.; Crane, R.; Ogden, T.; Arnott, M. (1996). "Taste and odour threshold concentrations of potential potable water contaminants". Water Research 30 (2): 331–340. doi:10.1016/0043-1354(95)00173-5. Bibcode: 1996WatRe..30..331Y. 
  4. ↑ Hovander, t. Malmberg, m. Athanasia, L.; Malmberg, T.; Athanasiadou, M.; Athanassiadis, I.; Rahm, S.; Bergman, A.; Wehler, E. K. (2002). "Identification of Hydroxylated PCB Metabolites and Other Phenolic Halogenated Pollutants in Human Blood Plasma". Archives of Environmental Contamination and Toxicology 42 (1): 105–117. doi:10.1007/s002440010298. PMID 11706375. Bibcode: 2002ArECT..42..105H. 
  5. ↑ Marsili, R. (2000). "Solid-Phase Microextraction: Food Technology Applications". in Wilson, Ian D.. Encyclopedia of Separation Science. New York, NY: Academic Press. pp. 4178–4190. doi:10.1016/B0-12-226770-2/06791-0. ISBN 9780122267703. https://www.sciencedirect.com/science/article/abs/pii/B0122267702067910. "Over the last two decades, the incidence of mouldy and musty off-flavours in cork-sealed wines has increased significantly. 2,4,6-Trichloroanisole (TCA) has been identified as the primary chemical responsible for cork taint. The human olfactometry threshold for TCA is 4–10 ng L−1 in white wine and 50 ng L−1 in red wine. In the case of wine, a worldwide loss of roughly US$1 billion per year is attributed to cork taint." 
  6. ↑ These include Central and South America.
  7. ↑ 7.0 7.1 Spadone, Jean Claude; Takeoka, Gary & Liardon, Remy (1990). "Analytical Investigation of Rio Off-Flavor in Green Coffee". Journal of Agricultural and Food Chemistry 38: 226–233. doi:10.1021/jf00091a050.  Note, at best, this source states that 2,4,6-trichlorophenol is "the probable precursor of TCA".
  8. ↑ Pereira, Helena (2007-01-01), Pereira, Helena, ed., "Chapter 14 - Wine and cork", Cork (Amsterdam: Elsevier Science B.V.): pp. 305–327, ISBN 978-0-444-52967-1, https://www.sciencedirect.com/science/article/pii/B9780444529671500169, retrieved 2024-01-14 
  9. ↑ 9.0 9.1 Cravero, Maria Carla; Bonello, Federica; Pazo Alvarez, Maria del Carmen; Tsolakis, Christos; Borsa, Daniela (24 June 2015). "The sensory evaluation of 2,4,6-trichloroanisole in wines: The sensory evaluation of 2,4,6-trichloroanisole in wines" (in en). Journal of the Institute of Brewing 121 (3): 411–417. doi:10.1002/jib.230. https://onlinelibrary.wiley.com/doi/10.1002/jib.230. 
  10. ↑ Crane, Louise (22 March 2019). "Trichloroanisole: Cork taint" (in en). https://www.chemistryworld.com/podcasts/trichloroanisole-cork-taint/3010280.article. 
  11. ↑ With regard to circumstantial evidence, Spodone, et al., op. cit., note that Rio off-flavor is associated with "beans heavily infested with various fungi (Aspergilli, Fusaria, Penicillia, Rhizopus, etc.) and bacteria (Lactobacilli, Streptrococci)".
  12. ↑ NTP (National Toxicology Program). 2021. "2,4,6-Trichlorophenol", Report on Carcinogens, Fifteenth Edition. Research Triangle Park, NC: U.S. Department of Health and Human Services, Public Health Service. [https://web.archive.org/web/20220118142253/https://ntp.niehs.nih.gov/whatwestudy/assessments/cancer/roc/index.html?utm_source=direct&utm_medium=prod&utm_campaign=ntpgolinks&utm_term=roc15 nih.gov] DOI: https://doi.org/10.22427/NTP-OTHER-1003



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