Perhaps you’ve had the unpleasant surprise of opening a nice bottle of pinot noir, preparing your palate for a fruity bouquet but instead being assaulted with a wet dog stench, accentuated by notes of mold. Such is the peril of cork taint, which can send even the most strong-stomached sommelier running for the hills.
Scientists have fingered a prime suspect in cork taint: a compound called 2,4,6-trichloroanisole, or TCA, a carbon ring studded with chlorine, oxygen and hydrogen atoms. TCA can form as a byproduct of fungal or bacterial contamination, and frequently grows within natural corks that have been treated with bleach or chlorine-containing products.
But the signature stench of corked wine may not actually originate from TCA itself. In a new paper published in the Proceedings of the National Academy of Sciences, Osaka University researcher Hiroko Takeuchi and colleagues say they’ve found evidence that TCA actually turns off certain parts of your sense of smell.
Signs have pointed towards this conclusion before. Wine Spectator noted back in 2007 that at lower levels, TCA can “[strip] 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.”
Most wine experts assumed that TCA’s signature smell was causing the loss of flavor and the stench, but were at a loss to explain how very small amounts of the compound could make for a tainted bottle. In the course of their research, Takeuchi and his team took a hard look at what are called “olfactory receptor cells,” or ORCs, which are nerve cells that play a role in the sense of smell. In their initial experiments, the researchers used ORCs from newts.
Takeuchi and her team found that TCA blocked a particular molecular channel in the cell membranes of the ORCs, meaning that it can effectively block odors – and at a rate up to 1,000 times more effective than odor-blockers used by the perfume industry.
Next, the team turned to 20 human volunteers – all experienced food tasters, but not wine tasters. The participants sampled red and white wines that had variable concentrations of TCA added in by the researchers. Some subjects could detect a TCA taint when the concentration was just 10 parts per trillion – equivalent to 10 droplets of the compound added to a volume of water equal to 20 Olympic-sized swimming pools.
“Unfortunately, we currently do not have a clear understanding of how extremely low concentrations of TCA can evoke a musty odor,” the authors wrote.
SOURCE: Takeuchi et al. “2, 4, 6-Trichloroanisole is a potent suppressor of olfactory signal transduction.” Proceedings of the National Academy of Sciences, published online 16 September 2013.