Corked wine is a generic -- and often inappropriate -- term used to describe wine that has been tainted. So-called "cork taint" is the most misunderstood and misreported issue in the wine world. Often based on anecdotes, the incidence of wine taint has been blamed almost exclusively on cork closures. But the hard evidence firmly demonstrates that "cork taint" is no longer a widespread problem.
First, let’s define taint. The taint typically associated with wine corks is TCA (2,4,6-trichloroanisole). It’s is a harmless but ubiquitous environmental compound that gives wine a musty flavor at very low concentrations (parts per trillion).
While TCA does come from cork, it also comes from sources such as contaminated winery or bottling equipment, airborne molds or chlorine-based compounds in wineries and cellars. A 2010 study scheduled for publication in the peer-reviewed American Journal of Agriculture and Food Chemistry, for example, looks at how wine barrels may introduce TCA.
Wine can be spoiled for many reasons unrelated to cork or TCA. Oxidation, a common problem with plastic stoppers, can make wine smell like candy banana flavoring. Numerous bacteria and molds can also spoil wine by making it taste like everything from rancid butter to sauerkraut.
But when wine fails to meet expectations, the cork gets blamed. Indeed, a recent study of 3,000 wine drinkers found that one in 20 complained that their wine was “corked” when in fact it had come from a bottle with a screw-cap.
The habit of blaming cork may explain why estimates of TCA contamination based on anecdotal evidence range from 2 percent to 10 percent and above. But a large and growing amount of hard evidence concludes that the incidence of TCA has dropped precipitously in recent years and is commonly measured at less than 1 percent of wines sealed with real cork.
- In 1999, before the introduction of numerous improvements to cork processing, wine chemist John Casey estimated the likely incidence of TCA at below 2 percent of all wines made in Australia. Casey based his analysis of the results of 19 studies involving over 35,000 wine samples.
- In 2002, a survey of 5,735 bottled wines conducted by the UK Wine and Spirit Association verified that only 0.6 percent had TCA contamination.
- In a trial by Southcorp in Australia involving 150,000 corks over nine years, the overall incidence of different types of cork taint was just 1.84 percent. Of this, 1.5 percent was due to TCA. (Simpson, RF, DL Capone, BC Duncan and MA Sefton, ‘Incidence and nature of “fungal must” taint in winecorks’, Aust. & NZ Wine Industry Journal, Jan-Feb 2005)
- Christian Butzke, Ph.D., one of the leading wine experts in the U.S. and a vocal critic of cork taint, stated: “TCA is no longer a major problem for the U.S. wine industry.” His findings at the Indy Wine Competition found cork taint to occur at levels at or below 1%.
- In a test of 500 bottles of wine, some of which included older vintages that would presumably have a higher incidence of TCA contamination, the French Wine Society found that four bottles – or 0.8 percent – were affected by TCA. The Society declared TCA a “non-issue.”
- Internationally renowned wine critic Robert Parker conducted a grenache tasting in late 2009 for almost 600 guests at Spain’s WineFuture. Less than 1 percent of the wine was affected by TCA.
- TCA levels are now 81% lower compared to levels found in 2001, according to the testing of more than 10 million corks by the Cork Quality Council.
The decrease in the incidence of TCA is largely due to improvements implemented by the cork industry. The industry has two complementary approaches used simultaneously for dealing with TCA. The first is to use quality control measures to prevent contaminated cork from being processed into closures. The second, which is the “curative approach,” is to assume that TCA will be present and then to remove it. The results of the above studies indicate that these efforts have been a resounding success.