Cork taint

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This article talks about TCA, aka Tricloroanisole.

Chemical structure of 2,4,6-trichloroanisole (TCA), the compound primarily responsible for cork taint 2,4,6-Trichloroanisole.svg
Chemical structure of 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 wine fault [1] arising from the presence of 2,4,6-trichloroanisole (TCA), a chemical compound that represents one of the strongest off-flavors, and one "generated naturally in foods/beverages", in particular wines, that considerably reduces the quality of these products. [2] [ better source needed ]

Contents

Cork taint is characterized by a set of undesirable smells or tastes found in a bottle of wine, especially spoilage that can only be detected after bottling, aging and opening.[ not verified in body ] Though modern studies have shown that other factors can also be responsible for taint—including wooden barrels, 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-trichloroanisole (TCA) or 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 ] It is created when some fungi are treated with chlorinated phenolic compounds,[ dubious ] 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 (2,4,6-trichlorophenol), a solvent used for industrial cleaning.[ citation needed ] [3] Bacteria is able to de-toxify TCP, notably Pseudomonas and Stenotrophomonas, but both strains cannot de-toxify the TCP without the other. [ 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 guaiacol, geosmin, 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 0.71.2% 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 1.02.0 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. [8] [ better source needed ] This occurs when wine barrels, drain pipes, wooden beams in the cellars, or rubber hoses are tainted by TCA. [8] [ better source needed ] Sometimes entire cellars have to be rebuilt in order to eliminate all potential systemic TCA culprits. [8] [ 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 wine chemistry at 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. 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. Bibcode:2013PNAS..11016235T. doi: 10.1073/pnas.1300764110 . ISSN   1091-6490. PMC   3791788 . 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. Gallego, Alfredo; Gemini, Virginia; Rossi, Susana; Fortunato, María S.; Planes, Estela; Gómez, Carlos E.; Korol, Sonia E. (2009-12-01). "Detoxification of 2,4,6-trichlorophenol by an indigenous bacterial community". International Biodeterioration & Biodegradation. 63 (8): 1073–1078. doi:10.1016/j.ibiod.2009.09.002. 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. 1 2 3 4 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)

Related Research Articles

TCA may refer to:

<span class="mw-page-title-main">Cork (material)</span> Tree bark tissue harvested for commercial use

Cork is an impermeable buoyant material. It is the phellem layer of bark tissue which is harvested for commercial use primarily from Quercus suber, which is native to southwest Europe and northwest Africa. Cork is composed of suberin, a hydrophobic substance. Because of its impermeable, buoyant, elastic, and fire retardant properties, it is used in a variety of products, the most common of which is wine stoppers.

<span class="mw-page-title-main">Tap water</span> Water supplied through a pipe and tap combination

Tap water is water supplied through a tap, a water dispenser valve. In many countries, tap water usually has the quality of drinking water. Tap water is commonly used for drinking, cooking, washing, and toilet flushing. Indoor tap water is distributed through indoor plumbing, which has existed since antiquity but was available to very few people until the second half of the 19th century when it began to spread in popularity in what are now developed countries. Tap water became common in many regions during the 20th century, and is now lacking mainly among people in poverty, especially in developing countries.

<span class="mw-page-title-main">Winemaking</span> Production of wine

Winemaking or vinification is the production of wine, starting with the selection of the fruit, its fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over millennia. There is evidence that suggests that the earliest wine production took place in Georgia and Iran around 6000 to 5000 B.C. The science of wine and winemaking is known as oenology. A winemaker may also be called a vintner. The growing of grapes is viticulture and there are many varieties of grapes.

<span class="mw-page-title-main">Corkscrew</span> Kitchen tool for drawing corks from wine bottles

A corkscrew is a tool for drawing corks from wine bottles and other household bottles that may be sealed with corks. In its traditional form, a corkscrew simply consists of a pointed metallic helix attached to a handle, which the user screws into the cork and pulls to extract it. Corkscrews are necessary because corks themselves, being small and smooth, are difficult to grip and remove, particularly when inserted fully into an inflexible glass bottle. More recent styles of corkscrew incorporate various systems of levers that further increase the amount of force that can be applied outwards upon the cork, making the extraction of difficult corks easier.

<i>Brettanomyces</i> Genus of fungi

Brettanomyces is a non-spore forming genus of yeast in the family Saccharomycetaceae, and is often colloquially referred to as "Brett". The genus name Dekkera is used interchangeably with Brettanomyces, as it describes the teleomorph or spore forming form of the yeast, but is considered deprecated under the one fungus, one name change. The cellular morphology of the yeast can vary from ovoid to long "sausage" shaped cells. The yeast is acidogenic, and when grown on glucose rich media under aerobic conditions, produces large amounts of acetic acid. Brettanomyces is important to both the brewing and wine industries due to the sensory compounds it produces.

<span class="mw-page-title-main">Malolactic fermentation</span> Process in winemaking

Malolactic conversion is a process in winemaking in which tart-tasting malic acid, naturally present in grape must, is converted to softer-tasting lactic acid. Malolactic fermentation is most often performed as a secondary fermentation shortly after the end of the primary fermentation, but can sometimes run concurrently with it. The process is standard for most red wine production and common for some white grape varieties such as Chardonnay, where it can impart a "buttery" flavor from diacetyl, a byproduct of the reaction.

<span class="mw-page-title-main">2,4,6-Trichloroanisole</span> Chemical primarily responsible for cork taint in wines (TCA)

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.

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 may arise from a "chemical or a microbial origin", where particular sensory experiences might arise from more than one wine fault. Wine faults may result from poor winemaking practices or storage conditions that lead to wine spoilage.

<span class="mw-page-title-main">Wine cork</span> Stopper used to seal wine bottles

Wine corks are a stopper used to seal wine bottles. They are typically made from cork, though synthetic materials can be used. Common alternative wine closures include screw caps and glass stoppers. 68 percent of all cork is produced for wine bottle stoppers.

<span class="mw-page-title-main">Alternative wine closure</span> Alternative methods for wine closure

Alternative wine closures are substitute closures used in the wine industry for sealing wine bottles in place of traditional cork closures. The emergence of these alternatives has grown in response to quality control efforts by winemakers to protect against "cork taint" caused by the presence of the chemical trichloroanisole (TCA).

<span class="mw-page-title-main">2,4,6-Trichlorophenol</span> Chemical compound

2,4,6-Trichlorophenol, also known as TCP, phenaclor, Dowicide 2S, Dowcide 2S, omal, is a chlorinated phenol that has been used as a fungicide, herbicide, insecticide, antiseptic, defoliant, and glue preservative. It is a clear to yellowish crystalline solid with a strong, phenolic odor. It decomposes on heating to produce toxic and corrosive fumes including hydrogen chloride and chlorine.

This glossary of winemaking terms lists some of terms and definitions involved in making wine, fruit wine, and mead.

<span class="mw-page-title-main">Clarification and stabilization of wine</span> Wine clarification and stabilisation

In winemaking, clarification and stabilization are the processes by which insoluble matter suspended in the wine is removed before bottling. This matter may include dead yeast cells (lees), bacteria, tartrates, proteins, pectins, various tannins and other phenolic compounds, as well as pieces of grape skin, pulp, stems and gums. Clarification and stabilization may involve fining, filtration, centrifugation, flotation, refrigeration, pasteurization, and/or barrel maturation and racking.

<span class="mw-page-title-main">Storage of wine</span>

Storage of wine is an important consideration for wine that is being kept for long-term aging. While most wine is consumed within 24 hours of purchase, fine wines are often set aside for long-term storage. Wine is one of the few commodities that can improve in flavour and value with age, but it can also rapidly deteriorate if kept in inadequate conditions.

<span class="mw-page-title-main">Screw cap (wine)</span> Cap for wine bottles

A screw cap is a metal, normally aluminium, cap that screws onto threads on the neck of a wine bottle, generally with a metal skirt down the neck to resemble the traditional wine capsule ("foil"). A layer of plastic, cork, rubber, or other soft material is used as wad to make a seal with the mouth of the bottle. Its use as an alternative to cork for sealing wine bottles is gaining increasing support. In markets such as Australia and New Zealand screw caps on bottles have overtaken cork to become the most common means of sealing bottles.

<span class="mw-page-title-main">2,4,6-Tribromoanisole</span> Chemical compound

2,4,6-Tribromoanisole (TBA) is a chemical compound that is a brominated derivative of anisole. It is one of the chemicals responsible for cork taint.

Nomacorc is a company producing engineered synthetic corks for wine bottles. Nomacorc closures are co-extruded to manage the oxygen transfer rate for wine, reducing 2,4,6-trichloroanisole (TCA), more commonly known as cork taint.

Adsorbable organic halides (AOX) is a measure of the organic halogen load at a sampling site such as soil from a land fill, water, or sewage waste. The procedure measures chlorine, bromine, and iodine as equivalent halogens, but does not measure fluorine levels in the sample.

A beerfault or defect is a flavour deterioration caused by chemical changes of organic compounds in beer, either due to improper production processes or storage. Some chemicals that can cause flavour defects in beer are aldehydes, lipids, and sulfur compounds. Small fluctuations within fermentation byproducts can have a huge impact on the flavour. When the concentration of one or more of these chemicals exceeds the standard threshold, the flavour characteristics change, creating a flavour defect.

References