If you open a bottle of wine and find your nose greeted by a smell reminiscent wet dogs, soggy cardboard or musty, dank old newspapers, you have opened a corked bottle of wine. Corked or corky wine principally gets its off-odor from a small aromatic organic chemical compound know as 2, 4, 6-trichloroanisole (TCA). The accompanying figure depicts TCA as a six carbon hexagon with a methylated oxygen attached at the number one position with three chlorines attached (Cl) at the 2, 4 and 6 positions. This small aromatic compound is volatile meaning it will easily fly out of solution at room temperature. Once TCA flies out of solution it can end up in your nose.

         The human nose contains an incredible ability to detect TCA at very low concentrations. In fact, the threshold for detection by the human nose varies in the literature 10-50 parts per trillion (ppt) to as low as 1 ppt. Literally this means that one TCA is detectable by the nose out of nearly a trillion air molecules. Clearly, very little TCA spells bad news for wine. TCA not only smells badly but will actually mask the pleasant aromas we enjoy in wine rendering it undrinkable.

         Estimates vary that from 2-5% of wine produced today suffers from cork-taint costing the wine industry over $10 billion. Where does this foul smelling TCA come from? There are three main sources of TCA contamination--making wine from moldy grapes, storing wine in barrels that have molded, and most significantly using moldy corks. The last source of TCA is by far the most common. The mould in corks produces TCA by metabolizing the toxic compound trichlorophenol into the non-toxic but smelly TCA. The toxic precursor trichlorophenol comes from chlorine used to clean corks reacting with the natural phenols such as tannins found in wine and wood. A variety of fungi including Penicillium and Trichoderma consume the trichlorophenol and use their metabolism to make it into TCA.

          The noxious smell of TCA belies its low toxicity. In fact, trichlorophenols have been used as microbicides in the US until banned by the USDA. Trichlorophenol is nearly a million times more toxic to some fungi than TCA. In some respect, the fungi are detoxifying the trichlorophenols and doing the wine consumer a favor. In the case where fungi are producing TCA, they in effect prevented you from drinking trichlorophenol, which apart from being toxic to fungi is also considered an environmental toxin and a suspected human carcinogen.

         Wineries fear TCA contamination because so little TCA is needed to cause an off odor in wine. Gallo Sonoma a few years ago reported cork taint in their bottling facility. Often the press implies that cork-taint equals a nearly insurmountable contamination situation. To get a realistic assessment of cork taint contamination, I spoke with Dr. Terry Acree in the Department of Food Science at Cornell University’s New York State Agricultural Experiment Station in Geneva, NY. He pointed out that the chemistry of TCA is quite simple. TCA is a small hydrophobic chemical that cleans up well with soap and water. Cork taint requires three components—phenolics, chlorine, and fungus. With proper techniques to control fungus using fungicides and proper cleaning of the contaminated areas with soap and water, TCA cleans up nicely.

         Controlling TCA contamination in a winery is one thing, but is it possible to recover TCA contaminated wine? TCA contaminated wine also cleans up nicely when passed through an activated charcoal filter. However, the problem with activated charcoal is that it will also grab all of the pleasant aromas from the wine leaving a rather simple beverage. One company called Vinterus claims to have developed an activated charcoal system that has been “tuned” to only remove only foul smelling aromatics thereby scrubbing the wine of TCA and the likes. They also claim that this system works equally well with white, red and sparkling wine. I learned of this company on the web, and they offer solutions to TCA contamination ranging from a pump system for decontaminating a single bottle of wine to large-scale devices for industrial scale jobs. More details were not available on the web and the contact number given for Vinterus had been disconnected. Perhaps this does not bode well for the effectiveness of TCA from corky wines. In the end, wineries may just have to suffer the off chance of a corky bottle or choose to close their wines with synthetic corks to avoid the risk all together. TCA contamination is controllable especially with careful techniques and more so with synthetic corks, but somehow a bottle of champagne with a plastic cork or a bottle cap seems a little less exciting.