Wine lovers dread "cork taint", the mildewy, wet-garage-full-of-old-newspapers odour that ruins a freshly opened bottle of wine. But the chemical responsible for cork taint's foul smell may actually work by numbing your nose's scent receptors. Huh?
2,4,6-Trichloroanisole (TCA for short, and the stuff that ruins your cabernet) occurs when natural cork fungus inadvertently contacts chlorine cleaning products during wine bottling. Since TCA was discovered in the 1990s, scientists assumed it worked like any other bad-smelling compound, stimulating scent receptors in the nose to send a stinky signal to your brain.
But when Osaka University's Hiroko Takeuchi and colleagues measured how isolated olfactory receptor cells respond to TCA, they found that, instead of stimulating activity in the scent-sensing cells, the compound knocked out the cells' electrical signals. In other words, when you "smell" cork taint, you're actually experiencing the numbing of your scent receptors.
Human testing supported this new, seemingly illogical finding; subjects reported that musty-smelling, TCA-tainted wine had a weaker overall aroma, even at TCA concentrations as low as four parts per trillion. The researchers also found TCA in a variety of foods including bananas, chicken, nuts, beer, whisky and tap water, and in non-edibles like paper bags, building material and resin used to make computer components — especially, they say, in products "judged to be of low quality".
It's still unclear why a compound that knocks out our sense of smell makes us think we're smelling wet dog. The team's best guess is that the reduction of activity in scent-sensing cells "may induce some kind of pseudoolfactory sensation" — in other words, a phantom smell. Winemakers have removed chlorine cleaning products from their bottling process, and many have switched to synthetic corks, but connoisseurs' love of vintage bottles means cork taint will continue to ruin much-anticipated uncorkings of decades-old vino.
Now that we know how this powerful nose-knockout compound works, maybe we can put its strange capabilities to use to block nasty odours. In the meanwhile, if you happen to open a tainted bottle, take a deep whiff — that's science you're smelling. [Livescience]