Wine Flaws: Corked?

Wine Spectator’s James Laube explains what a “corked” bottle of wine is in the below excerpt from its extensive website.  Learning to identify a corked bottle of wine comes with some experience, but once you are able to identify the signs and smell of cork taint you will be able to identify it when it presents itself.  

Wine Flaws: Cork Taint and TCA

James Laube, Wine Spectator staff
Posted: January 9, 2007

You’ve opened a bottle of wine that’s supposed to be outstanding. But when you put your nose to the glass, it smells like something you pulled out from a forgotten corner of a damp basement. What’s the problem? Most likely it’s TCA.

What is it? 
TCA stands for 2,4,6-trichloroanisole, a chemical so powerful that even in infinitesimal amounts it can cause musty aromas and flavors in wines. The compound forms through the interaction of plant phenols, chlorine and mold. It most frequently occurs in natural corks (TCA can even form on tree bark) and is transferred to the wine in bottle–which is why wines with these off-aromas are often called “corky.” But the taint can originate elsewhere in wineries, where damp surfaces and chlorine-based cleaning products are commonplace; barrels, wooden pallets, wood beams and cardboard cases are all sources of phenols. If TCA goes undiscovered, it can spread and eventually taint the wines.

How do I recognize it? 
Although TCA taint poses no health concerns for wine drinkers, it can ruin a wine. At higher levels, it makes a wine smell moldy or musty, like cardboard, damp cement or wet newspapers. At its worst, the wine is undrinkable. At lower levels, TCA taint merely strips a wine of its flavor, making normally rich, fruity wines taste dull or muted, without imparting a noticeable defect. This can leave drinkers disappointed in a wine without being able to pinpoint why.

Experts say people vary widely in their ability to perceive TCA in wine, depending on their genetics and experience. Some cork producers claim that levels of 6 or even 10 parts per trillion (ppt) are acceptable, as many people won’t notice TCA at this level. However, research in Europe and at the University of California, Davis, indicates that some tasters can detect TCA at 1 ppt to 2 ppt, and a rare few can perceive it at even lower levels. People with higher threshold levels may perceive an off characteristic without being able to identify it.

There is no legal standard for acceptable TCA levels in wine.

How common is it? 
As with thresholds of perception, estimates of TCA-taint frequency in vary widely. The number typically ranges from 1 percent to 15 percent of all wines, depending on whether it comes from closure manufacturers, vintners or another source. Wine Spectator’s Napa office tracks the number of “corky” bottles in tastings of California wines, and the percentage of defective corks routinely runs at 15 percent. At the magazine’s California Wine Experience in 2004, the team of sommeliers who screened the wines for the seminars reported that the occurrence of “corky” bottles was 4 percent to 12 percent. The cork industry has a different estimate of cork failure: typically 1 percent to 2 percent.

Learning how to identify a corked bottle of wine is an important step in becoming an educated consumer of wine.

Joanie Hudson, Director of National and International Marketing, Santa Barbara Winery / Lafond Winery & Vineyards