Cork taint

Source: Wikipedia, the free encyclopedia.

This article talks about TCA, aka Tricloroanisole.

2,4,6-trichloroanisole
(TCA), the compound primarily responsible for cork taint

Cork taint is a broad term referring to an off-odor and off-flavor

better source needed
]

Cork taint is characterized by a set of undesirable smells or tastes found in a bottle of

storage conditions and the transport of corks and wine[not verified in body]—the cork stopper is normally considered to be responsible, and a wine found to be tainted on opening is said to be corked or "corky". Cork taint can affect wines irrespective of price and quality level.[not verified in body
]

The chief cause of cork taint is the presence of the chemical compounds

2,4,6-tribromoanisole (TBA) in the wine, which in many cases will have been transferred from the cork, but which also can have been transferred through the cork rather than from it.[not verified in body] TCA is a compound which does not occur naturally;[dubious – discuss] It is created when some fungi are treated with chlorinated phenolic compounds,[dubious – discuss] which are types of antimicrobial agents used in the processing of wood. This class of compounds is a chief factor responsible for the problem associated with mold liable to be found in corks; very small amounts of this compound, on the order of nanograms, can be responsible for this defect.[not verified in body
]

Corked wine containing TCA has a characteristic odor, variously described as resembling a moldy newspaper, wet dog, damp cloth, or damp basement;[not verified in body] in almost all cases of corked wine, the wine's native aromas are reduced significantly, and a very tainted wine is quite unpalatable, although harmless.[not verified in body] While the human threshold for detecting TCA is measured in the single-digit parts per trillion, this can vary by several orders of magnitude depending on an individual's sensitivity,[not verified in body] where the detection limit is also complicated by the olfactory system's particularly quick habituation to TCA, making the smell less obvious on each subsequent sniff.[not verified in body]

Precursor

The primary chemical precursor to TCA is TCP (

better source needed][4] Chlorinated phenols can form chemically when hypochlorous acid (HOCl, one of the active forms of chlorine) or chlorine radicals come in contact with wood (untreated, such as barrels or pallets).[citation needed] The use of chlorine or other halogen-based sanitizing agents is being phased out of the wine industry in favor of peroxide or peracetic acid preparations.[citation needed] Chlorine dioxide has not been shown to produce these spontaneous chlorophenols.[citation needed] Chlorine dioxide is a relatively new agent being used in the wine industry due to its obvious advantages, having shown no evidence of the possibility of TCA formation.[citation needed
]

Production

The production of TCA in cork or its transfer by other means into wine is complex, but most results when naturally occurring airborne fungi are presented with chlorophenol compounds, which they then convert into chlorinated anisole derivatives. Chlorophenols taken up by cork trees are an industrial pollutant found in many pesticides and wood preservatives, which may mean that the incidence of cork taint has risen in modern times. Chlorophenols can also be a product of the chlorine bleaching process used to sterilize corks (not in use anymore); this has led to the increasing adoption of methods such as peroxide bleaching.

TCA and TBA are responsible for the vast majority of cases of cork taint, but other less common and less known compounds that can cause different varieties of cork taint include

2-methylisoborneol (MIB), octen-3-ol and also octen-3-one
, each with its own particular aroma, but all considered objectionable in wine.

Estimated occurrence and industry response

The cork-industry group APCOR cites a study showing a 0.7–1.2% taint rate. In a 2005 study of 2800 bottles tasted at the Wine Spectator blind-tasting facilities in Napa, California, 7% of the bottles were found to be tainted.[5]

In 2013, the Cork Quality Council ran over 25 thousand tests. The results, compared with data from eight years ago, show a sharp reduction in TCA levels, of around 81 percent. In the last test, 90 percent of samples of natural cork stopper shipments showed values of under 1.0 ppt and only 7 percent had showed results of 1.0–2.0 ppt.[6]

Improvements in cork and winemaking methodology continue to strive to lower the incidence, but the media attention given to cork taint has created a controversy in the winemaking community, with traditional cork growers on one side and the makers of newer synthetic closures and screw caps on the other. Screw caps and synthetic corks, however, are thought to be prone to another aroma taint: sulphidisation. This may arise from the reduced oxygen supply which concentrates sulphurous smells arising from wines with universal preservatives, however it is more likely that these wines contain excessive/imbalanced amounts of sulphite based preservatives to begin with.[7]

Systemic TCA

Systemic TCA tainting occurs when TCA has infiltrated a winery via means other than cork and can affect the entire production of wine instead of just a few bottles.

better source needed][verification needed
]

Rubber hoses or gaskets have a high affinity for TCA and therefore concentrate TCA from the atmosphere; wine or water that subsequently passes through infected hoses can become tainted with TCA.[citation needed] Another possible means of TCA contamination is through the use of bentonite, a swelling clay preparation (smectite) used in treating wine for heat stability; bentonite has a high affinity for TCA and will absorb TCA and related chemicals in the atmosphere, so if an open bag of bentonite is stored in an environment with a high (1–2 ng/g or ppb) TCA concentration, TCA will be absorbed in the bentonite and transferred to the wine lot to which the bentonite is added.[citation needed]

It is notable that this systemic TCA will often impart a trace (1–2 ng/L or ppt) to the wine, which itself is not detected by most consumers.[according to whom?][citation needed] However, with this high baseline level of TCA in bottled wine, even the additional contribution of a relatively clean cork can elevate the TCA level in the wine above threshold levels (4–6 ng/L or ppt), rendering the wine "corked".[citation needed]

Wine Spectator has reported that such California wineries as Pillar Rock Vineyard, Beaulieu Vineyard, and E & J Gallo Winery have had trouble with systemic TCA.[8][verification needed]

Treatment

Filtration and purification systems now exist that attempt to remove the TCA from corked wine to make it drinkable again, though there are few means of reducing the level of TCA in tainted wine that are approved by the TTB (formerly BATF).[citation needed]

One method of removing TCA from tainted wine is to soak polyethylene (a plastic used for applications such as milk containers and plastic food wrap) in the affected wine; the non-polar TCA molecule has a high affinity for the polyethylene molecule, thereby removing the taint from the wine.[citation needed] The surface area of polyethylene needed to reduce the taint to sub-threshold levels is based on the TCA level in the affected wine, temperature, and the alcohol level of the wine.[citation needed]

Some vintners have used the so-called half and half mix of milk and cream to remove TCA from wine (the TCA in the wine is sequestered by the butterfat in half and half).[citation needed] The French company Embag markets a product called "Dream Taste", which uses a copolymer shaped like a cluster of grapesthat is designed to remove the TCA taint from wine.[citation needed]

As advocated by Andrew Waterhouse, professor of

University of California, Davis, this can be done at home by pouring the wine into a bowl with a sheet of polyethylene plastic wrap; for ease of pouring, a pitcher, measuring cup, or decanter can be used instead, and the 2,4,6-trichloroanisole will stick to the plastic in a process effective within a few minutes.[9]

See also

Further reading

Notes

  1. ^ A wine fault is a sensory-associated (organoleptic) characteristic of a wine that is unpleasant, and may include elements of taste, smell, or appearance, elements that arise from a "chemical or a microbial origin", where particular sensory experiences (e.g., an off-odor) might arise from more than one wine fault. See Watrelot, Aude; Savits, Jennie & Moroney, Maureen (2020). "Wine Fault Series" (PDF). ISU Extension and Outreach (Extension.IAState.edu). Ames, IA: Iowa State University (ISU). Retrieved June 26, 2023.{{cite web}}: CS1 maint: multiple names: authors list (link) See also Merriam-Webster. (n.d.). Organoleptic. In Merriam-Webster.com dictionary. Retrieved June 26, 2023, from https://www.merriam-webster.com/dictionary/organoleptic.
  2. PMID 24043819.{{cite journal}}: CS1 maint: multiple names: authors list (link)[non-primary source needed
    ]
  3. ^ https://www.epa.gov/sites/default/files/2014-03/documents/ffrrofactsheet_contaminant_tcp_january2014_final.pdf
  4. ISSN 0964-8305
    .
  5. ^ Laube, James, Wine Spectator (March 31, 2006) "Changing With the Times" Archived 2006-03-14 at the Wayback Machine
  6. ^ "CQC Audit Results". corkqc.com. CQC. March 2014. Archived from the original on 2014-09-26. Retrieved 2014-08-05.
  7. ^ Heald, Claire, BBC News Magazine (January 17, 2007). "Put a stop in it"
  8. ^ a b c d J. Laube Taint Misbehavin Wine Spectator pg 43 March 31st, 2007.
  9. ^ McGee, Harold, The New York Times: The Curious Cook (January 13, 2009). "For a Tastier Wine, the Next Trick Involves ..." The New York Times.{{cite news}}: CS1 maint: multiple names: authors list (link)

References

External links

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