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Report Claims Less Than 1 Percent of Corks Are Noticeably Tainted

Survey pleases the cork industry, but others dispute the findings

Stuart Fox
Posted: August 20, 2009

Wet dog. Old Sock. Moldy basement. It seems there's a litany of ways to describe the taste and aroma of cork taint. And, unfortunately, most wine drinkers have had plenty of chances to verify those descriptions of this common wine defect.

Yet despite still being one of the leading reasons for returned bottles, a new study suggests that cork taint now affects less than 1 percent of all wine bottles. The cork industry is of course pleased by the findings—Amorim, the Portuguese company that is the world's largest cork producer, was quick to trumpet them in a press release. Corked wine has cost the industry millions of dollars a year in business lost to alternative sealing methods.

But other scientists were quick to caution that the results were far from scientific, and that cork taint remains a major problem, despite industry efforts to reduce the rate of corked wine.

Corks are made from the bark of cork trees, and various fungi live inside the fine pores that give cork its light, springy structure. Certain conditions cause the fungi to produce various chemical compounds that can affect a wine's flavor. The most notable is 2,4,6-trichloroanisole (TCA). These compounds give the wine that musty, moldy flavor and aromas.

The cork industry has spent decades trying to eliminate TCA and its friends. When chlorine- and bromine-based pesticides sprayed on cork trees and chlorine bleaches used to wash cork planks were suspected of triggering the fungi, they were eliminated, but taint kept popping up. Now Amorim and other producers use various cleaning processes. Some test the corks with gas chromatography-mass spectrometry to detect TCA early on and reject the cork. While the industry says the methods have reduced the number of bad corks, others remain skeptical.

"It's been almost 60 years that the industry has had to fix the problem," said Christian Butzke, an enology professor at Purdue University and the author of the new study, "and now they are reasonably close to doing it."

Butzke bases his claim, which appeared in a recent issue of Vineyard and Winery Management, on his survey of the 2008 and 2009 Indy Wine Competition, one of the country's largest competitions, held in Indiana annually. Both years, 70 judges identified fewer than 1 percent of 3,300 wines they tasted as affected by cork taint.

Butzke admits that the survey did not meet the rigors of a scientific study, but others support the results. "Ten years ago, people said it was much higher. Five percent, higher, the numbers were all over the place," said Susan Ebeler, a chemist in the department of viticulture and enology at the University of California, Davis. "But I trust Dr. Butzke that the number is below 1 percent now."

The assertion runs counter to several analyses, however. A 2003 report in a French journal postulated that 5 percent to 8 percent of corks on that market were tainted. In 2005, Wine Spectator senior editor James Laube found that 7 percent of 2,800 bottles sampled during tastings that year were tainted. Laube recently reported similar findings this past year.

Yet research into the science of cork taint indicates that the two results may not be mutually exclusive. The explanation for that paradox revolves around TCA itself. According to Ron Jackson, author of Wine Science: Principles and Application, a person's ability to detect the presence of TCA varies so widely that the percentage of bottles identified as corked could swing wildly depending on who was doing the tasting.

According to Jackson, 99 percent of people can detect TCA at concentrations in the range of 200 to 300 parts per million. "But some people can detect concentrations as low as single parts per trillion," said Jackson. Unfortunately, even when TCA levels are too low to detect, they can ruin a wine—at low concentrations the chemical deadens a wine's fruity flavors and aromas.

A 2002 paper in the Journal of Agricultural and Food Chemistry further complicates the matter. According to that paper, human identification of cork taint did not correlate with detectable levels of TCA, calling into question tasters' ability to distinguish between cork taint and other forms of wine spoilage. So not every moldy, musty smell may result from a cork problem, even if that is where tasters lay the blame.

Jackson believes the level of cork taint may dramatically drop in a few years. Cork producers phased out chlorine pesticides in the '90s, but it takes a decade or more for the trees to regenerate their bark. Soon the entire cork harvest will be chlorine- and, hopefully, TCA-free. And as long as producers like Amorim are losing money to alternative closures, they'll continue to invest money in finding ways to clean up TCA for good.

Randolph M Loos
USA —  August 21, 2009 1:55pm ET
Wish it were true... my experience is in the 6-8% range. Hopefully the article is on point about the reduction in corks with TCA...
Bruce Nichols
Naples, —  August 21, 2009 10:42pm ET
Finally! I have often thought that many "corked" wines, were "off" but not necessarily due to TCA, marginally made wines to begin with, or handled poorly after they were bottled. Improper storage, VA, or any number of things can effect the final product. In my personal experience (30+ years) in the industry, at best taint has been an issue, maybe up to 3% at best. There are unstable wines out there, especially in the lower price tiers, but to suggest that it runs upwards of 7-10% as I've heard some claims is questionable.
That said, I am all for any wine that is meant to be consumed within the first five years, well - "screw them!"
Neil Monnens
San Francisco, CA USA —  August 23, 2009 7:28am ET
WineRelease.com just completed a wine closure survey with its consumer and winery trade. 33% of consumers thought cork taint to be 1-3% and 32% believed it was 4-6%. 46% of winery responses believed cork taint to be 1-3% and 28% said 4-6%.

Full results here: http://www.winerelease.com/Other/WineClosureSurveyJuly09/July2009WineClosureSurveyResults.html (or http://bit.ly/fcAtG)
Thomas D Nichols
Houston, TX —  August 25, 2009 12:56am ET
Not such a simple subject. I believe, just considering TCA, that age accentuates the problem. I am not sure why this happens, chemically. When you are tasting 20 year old bottles, it is very noticable. Definitely we should buy our Lafite, Gaja, Penfolds and Dunn with another seal.
Best regards, Tom Nichols in Houston
John & Ann Churchill
São Paulo SP Brazil —  August 25, 2009 3:24pm ET
I believe the cork makers know their product and direct worst corks (more TCA) to less sophisticated/vocal markets (like here in Brazil - where we don't export much). Cheaper corks also have a lot higher contamination rate than expensive corks - probably because they tend to be made up of many pieces of cork, any one of which could be contaminated and ruin the wine. The good news is that, yes, TCA is appearing less and less, the cork producers are getting their act together.

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