If you've ever opened a bottle of wine to discover something that smells like a mouldy hymn book and tastes even worse, you've made the acquaintance of a chemical compound called 2,4,6-trichloranisole. This may sound like a benign cross between an air freshener and a Tom Robinson single, but it's very annoying stuff. TCA, as it's known in spitting circles, is responsible for corked wines. (Incidentally, these have nothing to do with bits of cork floating on the surface, despite what know-nothings might tell you.)
All sorts of things can go wrong with a bottle of wine, from explosion to bacterial spoilage, but the most common fault is cork taint. Depending on which side you believe - the manufacturers of natural cork stoppers and of so-called alternative closures have been engaged in a propaganda war for the last decade - anything between one and 10 per cent of wines are corked. The problem with establishing a reliable figure is that 'corkiness' varies in intensity. In the most extreme cases it renders a wine undrinkable (though not physically dangerous); in others it just flattens its aromas and flavours.
TCA is a random taint, which can affect the finest château-bottled Bordeaux as easily as the cheapest plonk. (Well, not quite: the problem seems to be less prevalent in more expensive wines.) If you buy a bottle of wine that's corked, you should send or take it back immediately. Any decent supermarket, off-licence, wine merchant or restaurant should replace it without question. I say should, because I've had some spectacular run-ins with French waiters about corked wines. 'It is traditional, monsieur,' one sommelier told me. 'All the wines from this region taste like this.'
Where does TCA come from? The honest answer is that nobody really knows. It is probably, as the Oxford Companion to Wine puts it, 'caused by the action of chlorine on cork bark or wood' during the manufacture of corks, but efforts to eliminate it have met with only partial success. Many cork manufacturers have stopped using chlorine to bleach their corks, but the problem hasn't gone away. Some of them rightly argue that the taint can come from barrels or winery rafters as well as corks, but the image of natural cork has still suffered in recent years. So much so that the Portuguese cork association, APCOR, has just launched a major charm offensive in the UK.
For the time being, the majority of consumers prefer natural corks, considering them more traditional and aesthetically appealing. Yet the alternatives are gaining in importance. Roughly 8 per cent of all wines are now bottled with screwcaps or plastic stoppers. These have helped to eliminate the risk of cork taint in many inexpensive wines. All the same, the fact that plastic corks can be hard to remove from the bottle and that screwcaps are associated with basic Lambrusco (and worse) has made some producers wary of switching too quickly, especially for their best wines.
Last year saw a number of important initiatives, however. Plump Jack, a California producer, released a Napa Valley Cabernet Sauvignon with a screwcap at more than $100 and many high profile wineries in Australia's Clare Valley and in New Zealand switched to screwcaps for some or all of their production. My guess is that natural cork will always be the most popular closure. The difference is that people who don't like playing vinous Russian roulette, who want to drink clean, TCA-free wine every time, have a viable alternative.
