TCA stands for 2,4,6-trichloroanisole, a compound that forms when phenols interact with chlorine and mold. In addition to grapes, barrels, wooden pallets, wood beams and cardboard cases are all sources of phenols. TCA most frequently occurs in wines bottled with natural corks, which are sanitized with a solution made from chlorine. When the wine comes in contact with the cork, TCA develops, causing musty aromas and flavors in wines. That is why wines with these off-aromas are often described as “corked.”
Although TCA taint poses no health concerns for wine drinkers, even in infinitesimal amounts, it can ruin a wine. At higher levels, it makes a wine smell moldy or musty, like cardboard, damp cement or wet newspapers. Most who encounter high levels of TCA, realize it is the cause of the befouled wine. At lower levels, TCA taint only strips a wine of its flavor, making it taste dull or muted. This experience can leave the drinker with the conclusion that the wine is simply bad. At even the low-ball estimates by the cork industry of 1-2% effected bottles, TCA-taint is a major concern for the wine industry, and a major influence on the growing popularity of alternative closures.