Wine: Barry Smith

“Would you like to try the wine?” This seemingly innocent question from the waiter is an invitation for you to test whether the wine is fault free. But how can you tell? The most likely fault a wine might have is being corked, which tends to give it a damp, musty smell of wet cardboard. To be sure, ask to smell the cork itself, which is usually the best clue. But will you and the waiter agree about whether the offending odour is present? I’ve been given doubting looks on occasion, though good establishments will always give you the final say. People’s detection threshold for the culprit of cork taint—2,4,6 trichloroanisole, or TCA—varies widely. Some can detect three parts per trillion, while others require 24 parts. So while you might be able to smell the presence of TCA, the waiter might not.

Any odour whose detection we measure in parts per trillion is one of the most volatile substances our noses are exposed to—so it’s surprising to learn that some individuals are utterly immune to TCA. They have a selective anosmia (a gap in their ability to sense odours). We all have them, but what is more surprising is that at least two sensory scientists I know are anosmic with respect to TCA. Both work on wine and will happily drink those that the rest of us reject. This leads me to wonder just how many wine waiters might be in their position.

A more significant question, though, is whether the wine tastes as good to those who are immune to the smell of cork taint as it would were it fault free. For those who can detect it, the smell certainly contaminates the fruit and floral flavours in the wine. But is this because the flavours are less pronounced than normal or because the unpleasant off-note so dominates our attention that it is hard to appreciate how the wine would taste without the spoiling whiff of damp cardboard? Perhaps TCA interferes with the delicate chemistry that produces a wine’s characteristic aromas. Experienced tasters certainly believe that when a bottle underperforms, rendering the liquid dull on the nose and the palate, this can be caused by cork taint that isn’t yet displaying its telltale smell.

On the other hand, a new study by Hiroko Takeuchi and colleagues at Osaka University suggests that TCA doesn’t actually add an offending off-flavour or odour; rather, it suppresses our acuity in perceiving other odours by blocking receptor transmission. Perhaps the worry should not be about the individuals who are insensitive to TCA, but about the rest of us, who are susceptible to TCA’s effect on olfaction and are missing the real flavours.

It’s hard to buy this explanation in its entirety. Why should the TCA-induced inability to process certain odours result in all sufferers agreeing upon the same unpleasant smell of corked wines? (The authors hypothesise it is a phantom smell we all share.) If it is absence rather than presence that accounts for the odours of a corked wine, are we to believe that all wines at base smell of a damp cellar, and that this emerges only once we are denied the ability to smell other compounds? Like wine writer and biochemist Jamie Goode, I’m holding out for the claim that, whatever else TCA does, it still produces a characteristic off-note in cork-tainted wines.

Returning to our first question: how can you tell if your wine is really corked? If you are even in doubt about it, it probably is. If you’re in two minds, trust the signals that are leading you to wonder. If the replacement bottle gives rise to the same doubts, this may mean the whole case is contaminated. But to keep rejecting bottle after bottle, you won’t just need a good nose, but nerves of steel.