Cork taint

2,4,6-trichloroanisole

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 held to be the traditional scapegoat, 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.

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. Improvements in cork and winemaking methodology continue 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 powerful marketers of newer synthetic closures (such as Alcan's Stelvin® cap) on the other.

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

In late 2005 Cork Supply USA introduced the INNOCORK process that removes TCA from wine corks. INNOCORK is a unique process that uses a steam distillation treatment with ethyl alcohol to remove TCA, as well as other undesirable compounds, from natural wine corks. Besides removing TCA, the process greatly increases the overall neutral characteristics and consistency of processed cork lots. The amount of releasable TCA that INNOCORK removes varies with the amount originally in the corks. But research shows that in corks with 4 to 6 ng/L, the amount is 92 percent. For corks with 1 to 4 ng/L, the amount is 60 percent, and for corks with 1 ng/L or less, the amount is 65 percent. 6ng/L is generally accepted as the lowest threshold that most people can sense TCA and the INNOCORK process lowers TCA to below 1 ng/L. A TCA level below 1 ng/L can’t be measured with current technology.

See also

• Wine fault
• Flavor scalping

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