608 A. Bertrand and A.A. Beloqui
These compounds were not found in the wines studied. Nonetheless, some were
detected in a grape marc spirit with a clear reducing defect in which we detected the
presence ofcis-/trans-3,5-dimethyl-1,2,4-trithiolane andcis-/trans-3,6-dimethyl-
1,2,4,5-tetrathiane, although neithercis-/trans-4,7-dimethyl-1,2,3,5,6-pentatiepane
nor 1,1-ethanedithiol were detected. These compounds could possibly come from
the base wine used for the distillation, although it is prohibited to use SO 2 in wines
used for this purpose. The hypothesis according to which ethanal is free to react
with H 2 S is, therefore, reinforced.
In conclusion, high doses of hydrogen sulphide in wines caused by the late treat-
ment of vines with sulphur or some pesticides can cause serious defects in the grape
marc. Moreover, it is almost impossible to remove the products from the compounds
formed.
10.6 Cork Flavor
Cork flavor, or the olfactory defect caused by moulds, is the commonest of the
undesirable flavors found in wine. In most cases, the cork is responsible for taint-
ing wine with 2,4,6-trichloroanisol (TCA) (Tanner et al. 1981). However, barrelled
wine may also be contaminated with 2,3,4,6-tetrachloroanisol (TeCA) that can be
present in the damp atmosphere of wine cellars in the presence of woods treated
by polychlorophenols. TCA has a slightly different aroma than TeCA but the two
contaminants are often confused. Another possibility is that the cork itself may be
contaminated by other corks (TCA) or by TeCA.
Wines often have this defect and it can affect up to 5% of bottles.
10.6.1 Origin of the 2,4,6-Trichloroanisol (TCA)
When a wine is tainted with cork flavor and this effect is caused by TCA, this is
almost always caused by the cork. This can be verified by analysing the wine and
also the central third of the cork that cannot have been contaminated by either the
wine or by the exterior.
Consumers reject a wine containing more than 10 ng/L of TCA. Wine experts,
however, can detect this defect from levels of 5 ng/L and can even detect its negative
effects at levels of around 2 ng/L when comparing with an uncontaminated control
wine.
Two different cases of cork contamination can be observed.
when the cork material is the source of contamination, very high values can berecorded such as 1500 ng/g. These high values are almost always recorded when the
cork has high concentrations of trichlorophenol (TCP) (Table 10.1).
Several studies have shown that the main cause of this is treating the corks with
chlorine or bleach solutions. It has alsobeen demonstrated that when a wine is