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Bad Chemistry

Cork disease can taint wines

Every once in a while, a bottle of wine — even a very good wine, from a reputable producer — breaks bad. Excuses abound, but reasons are harder to find.

Bad chemistry. The sequence is predictable: We buy a decent wine, treat it well until we pull the cork. We pour the wine, bring it to our lips. First, we’re assaulted by nasty aromas: moldy, musty, damp basement, mildewed stacks of old newspapers … Descriptors vary. Flavors, too, remind us of soggy basements. If the condition is advanced, the wine is undrinkable.

That condition is known by various names: cork disease, cork taint, “corked.” Researchers have pinned a chemical name on this, the ugly backside of wine; they call the problem 2,4,6-trichloroanisole, or just TCA. Researchers have found that TCA results from a reaction between certain fungi and bacteria and the chlorine agents usually used to sterilize cork.

Looking back. Let’s stop for a brief history. Wine, we now believe, has been made and consumed for more than 3,000 years, and over those millennia winemakers have sought and used various systems for containing their wines and closing the containers in order to prevent spillage, first, and exposure of the juice to oxygen in the air (which ages the wine and promotes its evolution into vinegar, great on salads, not so good by the glassful).

Without going into extensive detail, let’s just note that ceramic containers have been used, some stuffed with straw, some closed with melted wax, even ground glass. The advent of the glass bottle as a container for wine evolved over centuries, from too fragile to thicker and stronger (better for transportation of wine), and it found a closure match in the mid-1600s. The answer was a piece of bark — cork, that is, from the bark of cork trees that grow mainly in Portugal and parts of Spain.

Sadly, cork presented its own problems, especially as wine production increased so dramatically over the past 100 years or so. To prevent bacterial and fungal infections transmitted from the cork to the wine, cork had to be sterilized. Forms of chlorine were often used. All too often, TCA resulted.

In the 1980s, TCA was being found in about 8 percent of wines; that’s about one bottle per 12-bottle case, much too high. Vintners scrambled for alternatives: synthetics, composites, glass tops, screw caps. Cork growers/producers also raced for solutions, trying to save their burgeoning business; at this time, they claim to have virtually eliminated TCA, mainly by changing sterilization agents. Today, TCA is rare.

Still, buyers occasionally encounter TCA — and don’t like it. Some wine producers have completely abandoned cork closures; for example, most producers in Australia and New Zealand have committed to screw caps. But that has created some other problems, mainly having to do with marketing, that lingering image thing, nagging because the Aussie and Kiwi wines are often top quality.

Wine producers have spent millions of dollars promoting wine as a product with panache, a drink consumed by people with some prestige and sophistication. Even proper pulling of a cork required some special tools and skills in their use. Producers and their marketers created the illusory link: High-quality (i.e., expensive) wine got corks; cheapo vino got screw caps. Mystique got wrapped — and trapped — in a mistake.

Especially in posh restaurants, guests expect certain rites in the ordering and opening of a bottle: maybe a bit of yakking about vintage and producer, often with a sommelier, maybe some sniffing of the cork (silly, unless sniffing the side of the cork, where sniffers might detect TCA early — or not), then the ritual tasting, pouring (or not — some diners get a buzz out of sending a bottle back, even if the wine is quite drinkable).

[Note: Just because there are some cork fragments floating in your bottle or glass does not mean the wine is “corked” (TCA-affected); same is true if you find crystals on the bottom of the cork — they’re harmless, and blameless when it comes to TCA. Legally, if you order a bottle of wine and the cork has been pulled, you bought it, unless it’s demonstrably “bad.” Of course, in a fine restaurant, a server or sommelier will simply take the bottle back and invite you to order another; if the wine is bad, they’ll simply stick the cork back in the bottle and return it to their distributor for a refund or replacement, no questions asked.]

None of the ritual makes sense if the bottle is closed with a screw cap: Unscrew the cap, pour the wine, drink. There’s no TCA involved. Enjoy your wine. Embrace the screw cap.

There’s still some argument about whether wines closed by screw caps might not age as gracefully as wines finished with a natural cork. Research continues on this question. But consumer habits might have some bearing here: Before the advent of cork closures, almost all wines were consumed during the year of the vintage; the wines didn’t keep well and certainly didn’t age well. The cork-and-bottle combination opened wine drinkers to a new experience, particularly the subtle changes in flavors and textures of matured wines.

Recent research, however, shows that very few wine-buyers expect to “cellar” their wine, keeping it for (sometimes) years before opening and drinking. In fact, data indicate that some 90-plus percent of a vintage will be consumed within a year of its release. In response to these market facts, some top-shelf producers insist on continued use of natural cork as their bottle closure; producers of lower-priced, ‘everyday’ wines are, more and more, choosing to make the change to screw caps, saving money, eliminating the TCA problem and encouraging consumers to drink up — and buy another bottle.

Home solution to taint. If you encounter cork taint at home, you can try this: Wad up some plastic wrap, put it in a bowl, pour the wine over the wad, let it sit briefly. Chemists say the nasty chlorine will adhere to chemicals in the plastic, eliminating nastiness. Or simply re-cork it and return it to seller, assuming you saved the receipt — and bought from a reliable wine shop. Last option, if others fail: Cuss, open a new bottle, enjoy.