What
is cork taint, and where does it come from? I have personally never experienced
or even heard of it, but when the enologist was talking about it at Barone
Ricasoli vineyards, I became intrigued.
It turns out that the Ricasoli winery actually tests many different
types of corks to see which ones have the best properties for their wine. If more than a couple of the corks from
the batch they ordered are not up to par, they send the entire order back. Who knew such an innocuous piece of
wood could ruin a good bottle of wine?
 |
| TCA |
 |
| TBA |
As
it turns out, there are two main chemicals that are found to be present in wine
with cork taint: 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole
(TBA). These chemicals are
responsible for the moldy, damp, or mildewy smells associated with cork taint
in a bottle of wine. These
chemicals can be introduced into the bottle of whine by or through the
cork. There are also cases of
systematic TCA introduction, in which case TCA affects an entire production
line of wine. Although the cork is
almost always blamed for wine taint, wine spoilage can also arise from
oxidation in the wine, unclean processing equipment, and bacteria.
The
corks that cause cork taint often contain chlorophenol that the cork tree has
taken up through the industrially polluted air (This just gives us another good
reason to be more environmentally conscious; we’ll have less ruined
wine!). These chlorophenols can
also be introduced into the cork through the bleaching and sterilization
process that they must undergo before use. These chlorophenols in the cork then come into contact with
natural, airborne fungi that convert the chlorophenols into taint-producing
TCA.
Production Process of TCA
One
of the solutions to cork taint that has been proposed is the use of synthetic
closures, like rubber corks.
However, this is not the best solution because the rubber corks cause problems
of their own. Rubber corks often
taint the aroma of the wine due to sulphidisation, which occurs because not
enough oxygen can get into the wine through the rubber cork. This does not happen as often in
wood-corked wine because the wood cork can act as a microfilter that allows
oxygen and other small molecules into the wine. The process is very similar to wine aging in wooden barrels
to allow small molecules to diffuse in and out of the wine.
There
is no real way to stop wine taint other than by testing the corks to be used in
the wine before corking an entire production line with them. There are ways to remove the
unpleasantness from a batch of tainted wine if it had been systematically
tainted. To do this, wineries (and
you too, if you encounter this problem) can soak something made of
polyethylene, like a milk jug, in the wine. The polyethylene attracts the nonpolar TCA molecules, which
can attach to the polyethylene to be removed when the plastic is removed.
Any
way you look at it, tainted wine, especially if it’s that expensive bottle you
were excited about drinking, is no fun.
There is not much that we can do to prevent wine tainting other than
through testing, and perhaps by decreasing pollution around cork trees (and
everywhere else). In spite of
that, at least we have a simple way of remedying the solution in our own homes
when we sit down, open a bottle of wine, and smell something like moldy
newspaper coming out of the bottle.
http://www.chemicalbook.com/ChemicalProductProperty_EN_CB7375976.htm
http://www.chemicalbook.com/Search_EN.aspx?keyword=2%2c4%2c6-TRIchloroANISOLE
http://en.wikipedia.org/wiki/Cork_taint
http://www.corktaint.com/
http://winesignofindia.wordpress.com/2012/02/21/cork-taint-in-wine-produced-by-246-trichloroanisole-tca/closure3/
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