Cork taint

2,4,6-Trichloroanisole
Chemical structure of 2,4,6-trichloroanisole
Chemical name	2,4,6-Trichloroanisole
Chemical formula	C7H5OCl3
Molecular mass	211.47 g/mol
CAS number	[87-40-1]
Density	? g/cm3
Melting point	60-62 °C
Boiling point	132 °C at 28 torr
SMILES	COc1c(Cl)cc(Cl)cc1Cl
Hazards
R/S statement	R: 22-36 S: 26
RTECS number	MFCD00000588
Disclaimer and references

Cork taint is a broad term referring to 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. Though modern studies have shown that other factors can also be responsible for taint – including wooden barrels, storage conditions and the transportation of corks and wine – the cork is normally considered to be responsible, and a wine found to be tainted on opening is said to be "corked".

The chief cause of cork taint is the presence of 2,4,6-trichloroanisole (TCA) in the wine. Corked wine containing TCA has a characteristic odor, variously described as resembling a moldy newspaper, wet dog, or damp basement. In almost all cases of corked wine the wine's native aromas are reduced significantly, and a very tainted wine is completely undrinkable (though harmless). 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. Detection is also complicated by the olfactory system's particularly quick habituation to TCA, making the smell less obvious on each subsequent sniff.

The production of TCA in wine is complex, but most results when naturally-occurring airborne fungi are presented with chlorphenol compounds, which they then convert into chloroanisole. Chlorphenols 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. Chlorphenols can also be a product of the chlorine bleaching process ironically used to sterilise corks, which has led to the increasing adoption of methods such as peroxide bleaching.

TCA is responsible for the vast majority of cases of cork taint, but other less common and less known compounds that can cause different varieties include guaiacol, geosmin, 2-methylisoborneol (MIB), octen-3-ol and octen-3-one - each has its own aroma, all of them considered objectionable in wine.

Estimated occurrences of "Cork Taint" and Reactions

The incidence of bottles with cork taint is estimated to be between 1 and 15 percent. The former figure is from the cork-industry group APCOR, which cites a study showing a 0.7-1.2% taint rate. Anecdotal evidence from wine professionals suggests that the rate may be substantially higher. 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.

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 winemaking, with traditional cork growers on one side and the makers of newer synthetic closures and screwcaps (such as Alcan's Stelvin® cap) on the other.

There are now filtration and purification systems available which attempt to remove the TCA from corked wine to make it drinkable again.

See also

• Wine fault
• Flavor scalping
• Alternative wine closures

References

• Buser HR, Zanier C, Tanner H (1982). "Identification of 2,4,6-Trichloroanisole as a Potent Compound Causing Cork Taint in Wine". Journal of Agricultural and Food Chemistry. 30: 359–382.{{cite journal}}: CS1 maint: multiple names: authors list (link) DOI
• Tindale CR, Whitefield FB, Levingston SD, Nguyen THL (1989). "Fungi Isolated from Packing Materials - Their Role in the Production of 2,4,6-Trichloroanisole". Journal of Science of Food and Agriculture. 49: 437–447.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Pirbazari M, Borow HS, Craig S, Ravindran V, McGuire MJ (1992). "Physical-Chemical Charactarization of 5 Earth-Musty-Smellin Compounds". Water Science and Technology. 25: 81–88.{{cite journal}}: CS1 maint: multiple names: authors list (link)

External links

• Article on corked wine