TCA

One of the most frustrating aspects of wine is the number of bottles that are faulty. A well-made beer or spirit tastes exactly like it should, while a wine, however well made, may taste nothing like it should. A faulty bottle of wine can be caused by a number of reasons, but the main one is TCA, a nasty chemical compound called in full 2,4,6-trichloronanisole. A wine affected by TCA tastes like wet cardboard, a musty room, nail varnish remover, and downright nastiness. Such a wine is often described as "corked," because the damage TCA causes comes from a reaction in the cork between penicillum mould (as found in blue cheese) and chlorine used in the sterilisation process.

The instances of corked wines came to a head in the 1990s, after a complacent cork industry failed to address the issue. Screwcaps and various types of synthetic cork were a response to the number of wines affected by TCA. New Zealand, as modern a wine country as there is, made a conscious decision in 2001 to reject corks and now just under 70% of wines are bottled under screwcap. Since the 1990s, however, the cork industry has certainly cleaned up its act - literally, as corks are no longer cleaned with chlorine, the main cause of TCA.

Estimates vary as to how much wine is corked. It may have been as much as 10% in the 1990s, falling to 5% today. Conscientious wineries should be aiming for 2%. That's still high - a winery producing 50,000 cases may be distributing 1,000 cases of corked wine despite their best efforts.

It requires a great deal of effort in combating TCA. Using screwcaps or thoroughly analysing corks may not be enough: it can be found in cardboard packaging, in the winery, even contaminating glass bottles. Also don't forget that if a wine has been stored badly - particularly in an overly warm or bright environment - it will also be faulty, regardless of how it's been stopped.

The number of corked wines is intimidating because the overbearing restaurant experience of a waiter pouring some wine for you to taste is for you to check whether the bottle is clean or faulty: determining whether that bottle is faulty or not requires skill, experience, and confidence. Often a bottle which a customer dislikes is faulty, but they lack the knowledge to describe it as such. Waiters and sommeliers can be too protective to admit that they are serving a corked wine - even though it's a regular and unavoidable part of the job.

I just undertook a test in which I smelt forty-five wines back to back. They were organised in rows of three, in which one was faulty and two were clean. The nine faulty wines had been deliberately tainted with TCA, but to various degrees. The hardest to detect had 1 part in a trillion; the easiest had 4 or more parts (most people can detect 7 parts per trillion - that's how potent TCA is). I spotted 8 of the 9 tainted wines, meaning I am now entitled to a certificate proving I am capable of detecting 1 part of TCA per trillion.

The organisers, Vinquiry, based in Sonoma County, claimed that spotting TCA is genetic, and certainly some people will find it naturally easier to spot than others. But I also think it's part of the experience of regularly tasting. Even if you're readily able to detect TCA, you still need to know how to describe it and distinguish it from a wine that's simply badly made. This is especially true of a wine that has the faint 1 part per trillion: spotting that small amount comes, I think, from the misfortune of regularly tasting corked wine.