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 Corked wine confuses smell receptors 
 
 Mixed signals Rather than having an intrinsically bad odour, the chemical that makes wine smell 'corked' is preventing normal smell signals from reaching the brain, finds a Japanese study. 
 
 The discovery, made in newts, also fits with smell tests done on human volunteers, according to a report in the Proceedings of the National Academy of Sciences. 
 
 The effect of TCA (2,4,6-Tricholoroanisole), the chemical culprit in corking, on smell receptors was being investigated by Dr Hiroko Takeuchi and Professor Takashi Kurahashi and colleagues of Osaka University, Japan. 
 
 The researchers had expected to find olfactory (smell) receptor cells in the newt that could detect TCA, but they couldn't find any. 
 
 "We applied TCA to more than 100 receptor cells ... but we didn't see any excitation," says Kurahashi. 
 
 Meddling with membranes 
 
 Instead, to their surprise, they found the chemical inhibited the firing of the newt olfactory receptor cells as they tried to pass messages on to the brain. This means that, regardless of the odour the cell detects, it can't forward the information. 
 
 All of the olfactory cells they measured were inhibited by TCA, and at "remarkably low" concentrations. In fact, even the application of an incredibly weak solution of TCA (10 attomolar), still caused a slight suppression of a cell's normal response. 
 
 So how is TCA switching off smells? Kurahashi thinks it gets absorbed by the lipid membrane of the olfactory cell where it interferes with the workings of an ion channel. If the ion channel isn't able to function, the cell can't relay its message. 
 
 But TCA concentrations are so low that it can't simply be blocking the channels. One TCA molecule appears to be able to knock out many ion channels, most likely by disrupting the lipid membrane that holds them in place. 
 
 "It's very similar to the way some anaesthetics work [but] it seems to work at even lower concentrations than local anaesthetics or other drugs," Kurahashi remarks. 
 
 TCA could have wide applications as a masking agent, able to switch off unpleasant odours, thinks Kurahashi. 
 
 "It could be very useful in the cosmetic industry and in hospitals and retirement homes to mask unpleasant smells," he says. 
 
 Musty smell remains a mystery 
 
 The discovery reveals that in 'corking', the normal wine smells aren't reaching the brain. But one thing yet to be explained, Kurahashi says, is the characteristic "musty smell" that people report when tasting wine with cork-taint. 
 
 In a separate experiment on 20 people, Kurahashi found that the concentrations at which they reported smelling TCA's musty odour were exactly the same as those at which they reported a loss of flavour in the wine. 
 
 "This means [smell] suppression may be related to the induction of the musty smell," he says. He thinks the musty smell may result from "some kind of pseudo-olfactory sensation" in the brain. 
 
 A smell that affects the system 
 
 "It's quite an elegant piece of research", comments Dr Alisha Anderson of the CSIRO's Food Futures Flagship. "It just shows how complex the olfactory system is." 
 
 "We've always thought that the receptors were the part interacting with things in the environment, but this shows that you need to think more broadly about that, because things in the environment can also affect the system in a different way." 
 
 "The main question still left open for me is - why are we still sensing what's going on as a musty odour?" 

 Ever send a bottle of wine back at a restaurant? If you weren't just being a pretentious snob, then it was probably because the wine seemed “corked”—had a musty odor and didn’t taste quite right. Most likely, the wine was contaminated with a molecule called 2,4,6-trichloroanisole (TCA), the main cause of cork taint. But a new study by Japanese researchers concludes that you do not smell TCA directly; rather, TCA blocks up your sense of smell and distorts your ability to detect odors. The findings could help the food and beverage industry improve its products and lead to less embarrassment for both you and your waiter. 
 
 Wine tasters are well aware that TCA can ruin a bottle of wine. “More experienced tasters can recognize TCA taint at the first sniff of an affected wine,” says Thomas Matthews, executive editor of Wine Spectator magazine. “However, some of our tasters are much more sensitive than others to the flaw and pick it up at much lower levels.” In some cases, wines that tasters said were OK to drink but that reviewers rated as inferior turned out to have small but detectable concentrations of TCA when subjected to laboratory analysis, Matthews adds. 
 
 Researchers had long assumed that contaminants like TCA activate nerve cells involved in smell called olfactory receptor cells (ORCs), although they have not been able to explain how even extremely low concentrations of the molecule produce the corked odor. So Hiroko Takeuchi, a biophysicist at Osaka University in Japan, and colleagues set out to see what's really going on when ORCs are exposed to TCA and similar contaminants. First, the team isolated ORCs from newts, whose ORCs are the largest among vertebrates and about three times as large as those of humans. The cells' size made it easier to measure electrical currents across an ORC’s outer membrane by puncturing it with a thin glass tube called a micropipette. Such electrical currents activate the cell and are carried by calcium ions entering the cell. 
 
 To the researchers' surprise, TCA did not stimulate calcium to flow across the cell membrane. Instead, it stopped the flow by blocking passages through the membrane, called cyclic nucleotide-gated (CNG) channels. TCA was up to 1000 times more effective in blocking CNG channels than other odor blockers sometimes used in making perfume, the researchers report today in the Proceedings of the National Academy of Sciences. 
 
 Turning to human subjects, the researchers recruited 20 volunteers from the Daiwa Can Co. in Tokyo, which manufactures packaging for foods and beverages. The volunteers were experienced at tasting for “off” flavors and odors but were not experts in wine tasting. The subjects tasted glasses of both red and white wines to which the researchers had added minute amounts of TCA. In double-blind tastings, the subjects recognized cork taint from TCA at concentrations as low as 10 parts per trillion. (They also detected similar levels of two other common wine contaminants.) 
 
 TCA and other contaminants don't activate your sense of smell directly but distort it, giving the sensation of a musty odor, the researchers say. They suspect that TCA inhibits only a subset of CNG channels and thus mixes up the signals sent to the brain. TCA is also found in apples, raisins, chicken, shrimps, peanuts, cashews, sake, green tea, beer, and whiskey, as well as in packaging for these products. So the food and beverage industry “has to pay attention to TCA contamination,” Takeuchi says. 
 
 The study still doesn't reveal how such small concentrations of TCA create the effect. The molecules cannot stopper the channels directly because the typical ORC has about 100,000 CNG channels but the lowest concentrations of TCA applied to the newt cells would supply only about 600 molecules to a cell. So one TCA molecule must be affecting a number of CNG channels simultaneously. Takeuchi and her colleagues hypothesize that TCA-like contaminants are probably absorbed into the fat layers that make up the cell membrane to cause widespread disruption of the channels. 
 
 The findings are “not totally surprising,” says Barry Ache, director of the Center for Smell and Taste at the University of Florida in Gainesville. Many other chemicals are capable of blocking ion channels, he says, and “there is reasonable, if not compelling, evidence that a reduction in excitation is as much a part of the olfactory [sense] as excitation itself.” He agrees that TCA might be able to exert its powerful effect by dissolving into the cell membrane. 
 
 So, the next time you send back a bottle of wine, tell the waiter that you have detected unacceptable levels of TCA. That—and a decent tip—might persuade him that you're not just being pretentious. 
 
 *Correction, 16 September, 6:18 p.m.: The last sentence of the seventh paragraph initially began, "Takeuchi and his colleagues," when it should have read, "Takeuchi and her colleagues," as Hiroko Takeuchi is a woman. This has now been corrected, and we apologize for the error. 

 Wines that have been contaminated with a chemical found in cork often smell musty, like moldy newspaper. 
 
 Editor's Note: This story was updated on Sept. 17 at 9:55 a.m. ET. 
 
 A buttery flavor with notes of raspberries, chocolate and … wet dog? 
 
 Open enough bottles of wine, and eventually, one will smell a bit "off." Corked wines have been contaminated by a chemical carried in the cork that produces a musty, unpleasant smell often described as soggy cardboard or wet dog. 
 
 Now, researchers have found corked wine may smell so bad because the chemical culprit, rather than producing a yucky odor, actually suppresses the drinker's sense of smell. 
 
 "The present findings not only reveal a likely mechanism of flavor loss, but also suggest certain molecular structures as possible olfactory masking agents," the researchers write in their study, detailed today (Sept. 16) in the journal Proceedings of the National Academy of Sciences. [The 7 (Other) Flavors Humans May Taste] 
 
 Bad smell 
 
 The main chemical responsible for corked wine's off-putting smell is a chemical called 2,4,6-trichloroanisole (TCA). TCA infiltrates wine when a fungus that normally infects cork comes into contact with bleaches or chlorine products used in wineries for sanitation. Even tiny concentrations of the contaminant can cause the fungus to produce TCA — hence the foul, musty smell, often described as moldy newspaper. 
 
 After the cause of the smell was identified in the 1990s, many wineries removed chlorine products from their cleaning regimen. 
 
 Most researchers assumed that TCA produced chemicals that created the unpleasant odor. 
 
 Suppressing smell 
 
 To test that idea, Hiroko Takeuchi, a researcher at Osaka University in Japan, and her colleagues measured the electrical response of the nose's olfactory receptors to the presence of TCA in the lab. 
 
 Oddly, the TCA didn't seem to trigger any of the odor-sensing receptors in the cells. Instead, the chemical seemed to suppress the primary olfactory receptor, called the cyclic nucleotide-gated (CNG) channels, which play a key role in converting chemical smell signals into electrical signals. 
 
 The brain seems to interpret this smell-receptor suppression as an unpleasant odor for some reason, the researchers suspect. 
 
 The researchers then asked 20 people to describe any reduction in odor in TCA-tainted wine compared to normal wines. In past studies, scientists had asked participants to describe the weird smells of corked wine, but when they asked participants specifically about missing smell, these participants reported reduced odor perception. 
 
 And in a follow-up experiment, the researchers found that TCA was often found in foods and beverages that had lost some of their odor. 
 
 The findings imply that TCA works by reducing odor sensing, rather than by creating a bad smell, and that suppressing the sense of smell can somehow lead the brain to create a false impression of an off-putting smell. 
 
 "Based on these observations, we propose that the reduction of CNG channel activity may induce some kind of pseudo-olfactory sensation by inducing an off-response," the researchers wrote. 
 
 The results could have implications for scientists trying to develop odor-masking agents, the researchers added. 
 
 Editor's Note: This story was updated to note that Hiroko Takeuchi is a woman, not a man. 
 
 Follow Tia Ghose on Twitterand Google+. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.
– Those fluent in wine-speak sometimes refer to a wine being "corked"—meaning it has a nasty, musty smell upon being opened and doesn't taste so hot, either. Scientists have long identified the culprit as a chemical in the cork known as TCA, but new research from Japanese scientists adds a bizarre twist: It turns out that TCA doesn't cause a funky odor, but nearly the opposite—it "actually suppresses the drinker's sense of smell," explains LiveScience. Even small amounts of the chemical distorts olfactory signals and blocks the usual wine scents from reaching the brain, reports Science. Unfortunately, the brain is left with what it interprets as a musty odor, for reasons that are still unclear. "It's quite an elegant piece of research," one scientist not affiliated with the study (on both newts and humans) tells Australia's ABC News. "It just shows how complex the olfactory system is." The discovery could have odor-blocking applications for the cosmetics and hospital industries. But, adds the scientist, "the main question still left open for me is—why are we still sensing what's going on as a musty odor?" (In other alcohol-science news, researchers determined that a man is essentially brewing beer in his own gut.)