Cork or No Cork? The Science of Sealing Wine Bottles

Screwcaps and synthetic cork are becoming more popular for sealing wine bottles. But how do they affect the chemistry of the wine?

Different materials are now being used to seal wine bottles.

When you uncork a bottle of wine this holiday season, you may not necessarily be removing a piece of cork. In recent years, winemakers have been opting for other materials to seal up wine bottles, such as synthetic cork and screwcaps. While it may seem much less romantic to unscrew a bottle or pop out a piece of plastic, research has found that these new materials do have advantages over natural cork.

For a winemaker, a corked bottle of wine is one of the biggest nightmares. Contrary to popular belief, being 'corked' has nothing to do with bits of cork floating in the wine. In fact, it means the cork is contaminated with a chemical taint called TCA (2,4,6-trichloroanisole). Although harmless to health, this is amazingly potent stuff, detectable to the palate at concentrations of six parts per trillion: a tablespoon of TCA could ruin the entire U.S. output this year. Found randomly in the bark of cork trees (which is what, after treatment, goes into the bottle), TCA imparts a musty, slightly moldy quality to the wine and suppresses fruit aromas.