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!