Researchers at Osaka University in Japan recently discovered that cork taint does not intrinsically smell bad. Rather, a chemical associated with cork taint suppresses signals from our noses to our brains, distorting the ability to detect odors. A paper detailing the research study, which was led by Hiroko Takeuchi, Hiroyuki Kato, and Takashi Kurahashi, has been published in the Proceedings of the National Academy of Sciences.
The main cause of cork taint is 2,4,6-trichloroanisole (TCA), a molecule which is a byproduct of fungal or bacterial contamination. Prior to this work, researchers assumed that TCA stimulated the olfactory nerve cells (ORCs)—cells which are involved in the process of smell. However, it was not clear how TCA produced the odor associated with cork taint. To better under understand this phenomenon, the research team conducted two studies, one involving newts and one involving humans.
First the team studied the impact of TCA on newt ORCs. Among vertebrates, newts have the largest ORCs—about three times as large as those of humans—making it easier for researchers to measure electrical currents in the cells. Researchers found that TCA inhibited the “firing” of newt ORCs as they tried to pass messages on to the brain. As a result, the cells could not forward information about the odors they detected to the newts’ brains. Previously, it had been believed that TCA induced the sensation of unpleasant odors by stimulating the ORCs.
The second study, which involved human subjects, focused on how they reacted to the presence of TCA in wine. In a series of double-blind tastings, participants were asked to taste glasses of red and white wine to which minute amounts of TCA had been added. The twenty participants, who worked for a food packaging company, were experienced at tasting for “off” flavors and odors, but they were not experienced “wine tasters.” Researchers found that aroma perception was reduced when TCA was present, and the concentrations at which the subjects reported smelling the musty odor associated with TCA were exactly the same as those at which they reported a loss of flavor in the wine.
As a result of these studies, the research team concluded that the “off-flavors” characteristic of food and beverages containing TCA is not the result of unpleasant odors produced by TCA; rather it is related to the suppression of signals from the nose to the brain. In the case of cork taint specifically, researchers hypothesize that when TCA prevents normal wine smells from reaching the brain, it interprets this as the unpleasant damp cloth and wet dog aromas traditionally associated with corked wine. The research team’s findings have significant implications for the food and beverage industry as TCA has also been found in apples, raisins, chicken, shrimp, peanuts, cashews, sake, green tea, beer, and whiskey. Based on this work, they hope to develop ways to deliberately weaken the nose’s sense of smell in order to mask bad odors in certain products.