Cork Taint – A Rave!
By Franz Scheurer
(Cork taint, 2,4,6 trichloroanisole or TCA can be detected by human senses at 5 parts per trillion or less and is the result of an enzymic reaction in common fungi like Aspergillus and Penicillium).
As just about everyone knows I
love spirits. I adore whisky and couldn’t imagine a life without Single Malts.
What’s that got to do with TCA I hear you say?
Well, let me tell you. I am sick
and tired of so called experts in the spirits arena (who really should know
better) who will tell you that there is no such thing as cork taint in spirits
as, and I quote one such ‘expert’: “there is no cork taint in whisky, the bugs
couldn’t survive in such high alcohol anyway”.
What a load of uninformed
bullshit… or is the marketing department speaking?
I have personally come across a
fair number of corked whiskies (and other spirits). It manifests itself much
the same way as it does in wine: light taint flattens the drink (sometimes only
discernible when one knows the spirit intimately), and is often passed over as
‘ah well, don’t like this one, won’t buy it again’ and the heavy taint which
leaves wet cardboard and a strong mustiness on one’s senses. I believe as much
as 5% of all spirits under cork are affected to one degree or another.
Now just because I believe TCA
exists in spirits does not mean I’m right. So I enlisted the one person’s help
who I believe is one of the most knowledgeable on the subject of cork taint in
Australia: Peter Godden of the Australian Wine Research Institute in South
Australia.
Here is what he had to say:
“TCA is a chemical molecule that
is ubiquitous in the environment. It is formed by microbial action, but once it
is formed it is there for good, so the bugs can be killed, and it makes no
difference. So this is not an issue of bugs being able to live in whisky, or in
wine for that matter.
TCA is very volatile and very
mobile, and cork has a strong affinity for it. TCA can be formed in cork as
early as the forest, let alone a myriad of possible points in the production
process, or in the distribution chain where product can be contaminated from
common environmental sources such as soil, wooden pallets or cardboard boxes.
I have seen several TCA tainted
malts over the last three years since I really started to get back into the
subject. I stress that this is a very small sample set, but I estimate that I
recognize it in about 3% of bottles. However, it is very likely to be present
in many more bottles at sub recognition threshold concentrations, as the
agglomerate type corks used in whisky bottles are likely to be contaminated
with TCA at the same rate as other agglomerate corks.
I know that one of the descriptors
for it in spirits is "green walnut". I can identify with this. Next
time you see 'green walnut' character, compare it with another bottle - I have
been able to do this a couple of times, and the two bottles were quite
different. TCA was probably the culprit.
We also have conducted detailed
investigations of TCA in Australian Brandy spirit on several occasions, and
have quantified the amount of TCA by GCMS analysis. We had a very big case
about three years ago, with a very high incidence of taint in a batch of
brandy, and some of the bottles had a very high in intensity as well - it was
obvious.
There are sources of TCA in wine,
and possibly spirits, other than cork. We most often see it in barrels. We used
to see, perhaps, three or four cases a year, but we have worked hard to alert
the industry to this and we now see fewer cases. Some of the big wineries and
some coopers routinely check a sample of barrels pre use. We have a batch of
about 100 such wood shaving samples from barrels in for commercial testing at
the moment. The next most common source is environmental contamination of
processing aids and additives, particularly filtration media, usually from
wooden pallets or poor storage facilities. Wood-lined shipping containers are
also a major source. This contamination is then transferred to wine.
Just today I came across a paper
in the Aug 2005 issue of the peer-reviewed journal "Journal of Bioscience
and bioengineering", relating to TCA in sake. They have traced it back to
the rice mash, and it appears, to "wooden tools" used in the process.
There is no reason why this couldn't happen with whisky”.
I rest my case!