The turn of the screw

Often, global industries are criticised for their use of non-renewable resources and practices which pollute the planet. The wine trade - a massive global industry - should be justifiably proud and protective of its record in at least one aspect of production and packaging: cork.

Cork is the ultimate renewable, sustainable resource. The bark of the Quercus subur (Cork Oak) can be stripped without harming the tree. Nine years later, the bark will have grown again to a thickness that allows another harvest. On average, cork trees live for 170 years.

Cork trees grow all over the western Mediterranean, particularly in Portugal, where cork is a major industry in its own right. The qualities of cork bark are uniquely suitable for stoppering a bottle of wine: its cellular structure make it elastic (so it keeps on forming a powerful seal over many years), impermeable to gas and liquids (so it keeps the wine in and the air out) and inert (so it doesn't taint the wine).

However, there has always been a problem with cork, resulting in a condition commonly known as "corked" wine. A corked wine smells pretty disgusting: like dirty old dishrags that have been left mouldering for a couple of years. This horrible fault that you may have found in a wine if you are unlucky is believed to begin during the process of turning the cork bark into a wine bottle cork. The cork is washed in a chlorine solution, and a chemical called Trichloranisole can form. It is Trichloranisole (or TCA) which gives the musty, mushroomy smell. When it contacts the wine, the wine becomes tainted and undrinkable.

For whatever reason, corked wines seem to have become more prevalent in recent years, and over the past decade or so, the cork industry has been under siege from a whole band of businesses and scientists lobbying for things to change. They are fighting back, and new processes are being invented that do away with chlorine washing, and therefore should do away with corked wines.

However, there is a deeper question being asked by some: why should we risk our wines being corked at all? Why do we continue to use this old fashioned and unreliable method of closing a bottle, when so many alternatives exist?

You will no doubt by now have come across bottles stoppered with synthetic corks. Often brightly coloured and obviously making a bold statement, these plastic-based corks are very common in sub-£5 wines, especially from the New World. Indeed, Marks and Spencer have well over half their range in plastic corks, believing this will cut down on consumer complaints and returned faulty bottles.

But synthetics are not without their critics either. For one, they have a nasty habit of destroying expensive corkscrews; their dense texture gripping the sides of the screw and stripping off the Teflon coating that makes them effective. But more of a doubt is cast over their long-term ability to securely close an expensive bottle of wine for laying down. Some Australian producers I've talked to have experimented and believe that some synthetic corks lose elasticity over a few years and allow oxygen to enter the bottle: the major enemy when trying to preserve a fine wine over many years.

Indeed, a whole band of winemakers are currently trying to persuade us that the ultimate answer is the humble screwcap as found on the very cheapest wines around.

From California, the Plumpjack winery has just released its premium Cabernet Sauvignon wine in a screwcapped bottle. Price? a cool £110.00. This is a very bold statement indeed, but Plumpjack believe discerning wine buyers will recognise that a screwcap is the perfect method of preserving their best wines: it cannot shrink; it cannot let in oxygen, and best of all, it cannot taint the wine.

Another bold move has been by the producers of Australia's most delicate wines, the high-quality Rieslings of the Clare Valley. A whole bunch of the very best producers have bottled a high proportion of their 2000 production in screwcaps (commonly called "Stelvins" over there). I've tasted some Stelvin-bottled Rieslings going back to the 1970's and there's no doubt they do a fine job.

So what does the future hold for corks and bottles? Well, there's something so satisfying about drawing a real cork from a fine bottle that it would surely meet massive consumer resistance if all wines were to come in screwcaps. And the cork manufacturers have woken up to the challenge of improving their product. In the future I can see the use of alternatives continuing to spread amongst lower-priced wines, but the natural cork will live on for quite some time.

Tom Cannavan is author of The Good Web Guide to Wine and publisher of wine-pages.com.
TC