For eight days in November, I was judging wine for the International Wine Challenge. As one of the co-chairs, I was tasting hundreds of wines a day. It raises the question: if you are tasting like this, does practice improve performance? Does working with your nose, whether you are mixing perfumes, blending wines, or cupping coffee, change the way you process smells?
Wine tasting is multimodal. Although in our conscious perception we experience the ‘taste’ of the wine, a lot of the information about the wine included in this ‘taste’ is coming from our sense of smell. When we initially sniff a wine, this is called orthonasal olfaction: we breathe in the volatile molecules and detect them in a small patch of tissue called the olfactory epithelium at the back of the nose.
Then when the wine is in the mouth, we also experience smell, this time retronasally: the volatiles access the olfactory epithelium from the backdoor route, as they enter the nose directly from the mouth.
We also get information from touch: the way that the wine feels in the mouth. All these sensations are combined in the brain before we are aware of them, and so the ‘taste’ of the wine isn’t just taste (in the strict sense) at all. In addition, our eyes tell our brain a lot about the wine and influence our perception – again, this happens before we are aware of the perception, and so it’s hard to unpick these different contributions to the overall sensation of flavour.
So smell is a very important part of the flavour of wine, and there is evidence that our performance can be enhanced by training.
People who have impaired sense of smell either through head trauma or viral infection (one of the symptoms of Covid-19 is loss or impairment of smell) have been shown to benefit from a smell training program (https://abscent.org/smell-training). There’s a really good explanation of the science behind this on the Fifth Sense website, which explains how this sort of training works (https://www.fifthsense.org.uk/smell-training)
Abnormalities of smell are far more widespread than most people realize. Loss of smell is a significant problem affecting about 5% of people (and it’s estimated that 20% of people have some sort of smell dysfunction). While we tend to think that if we are going to lose a sense, smell is the least bad one to lose, people who have suffered anosmia (the technical term for the loss of smell) really seem to miss it, and commonly suffer from depression.
What about wine tasters with no obvious impairments? Can their abilities be enhanced by repeated stimulation? It is an intriguing idea. I find I’m better at making quick judgements about wines after a few days of tasting, but this probably isn’t long enough to see any benefits from smell training kicking in. What about tasting wine every day for years? Does this change the way we smell?
One experiment that would be relatively easy to do and that could address this question, would be to take enology students and test them for thresholds to a range of wine-related aromas at the beginning of their course, and then repeat this testing at the end. It would be interesting to see whether their smelling ability has improved by a course in which they have been making intensive use of olfaction over a few years, and whether any improvement is general, or is specific to wine-related aromas.
There’s also the interesting question of exactly how performance is being improved by smell training. Is it at the receptor level, or is it the way that the information from the receptors is being processed in the brain?
Our olfactory receptor neurons each have one olfactory receptor type, and we have around 400 different olfactory receptors. This is where the brain meets the outside world, and it is one of the few brain structures where there is continual turnover and cell differention: these neurons regenerate every few months. This means that at the receptor level, it’s possible to recover from disorders such as infection or cell damage quite quickly.
This is where the case of androstenone is interesting. It is a steroid that occurs in sweat and urine in humans, and it is produced in high levels by pigs. Most of our 400 or so olfactory receptor genes respond to more than one smell molecule, but there are examples of specific anosmias resulting from mutations in single genes, and androstenone is one of these. The OR7D4 gene codes for an olfactory receptor protein that enables us to detect androstenone. Those who can smell it fall into two groups: some find it sweaty, urinous and musky (unpleasant), or they find it sweet smelling. Others can’t really smell it at all.
But there’s an interesting twist on the androstenone story. First, insensitivity to androstenone changes though adolescence, especially in males. Secondly, the ability to smell it can be induced by exposure, which is very surprising for a trait that has a strong genetic component. This was first observed by Wysocki and colleagues in 1989. How might this work? Of the people who initially can’t smell androstenone, Wysocki’s group found that some can acquire sensitivity to it by repeated exposure, and for those who can smell it, their threshold is lowered by the same treatment.
One theory, supported by some evidence, is that there are changes at the olfactory epithelium level (peripheral changes, involving the expression of the receptor for androstenone in olfactory receptor neurons). But this evidence is countered by work that exposes only one nostril to androstenone and sees changes in sensitivity in the other, suggesting a central mechanism further up in the brain processing pathways of smell.
There are a range of other odorants for which repeated exposure increases sensitivity. It would be really interesting to know how all this applies to wine tasting. Could we improve our tasting ability through smell training? And does our performance improve with practice, as the research done so far seem to suggest?
And how much do subliminal smells matter in wine tasting? There is intriguing research looking at how our moods and choices are altered by odorants that are below the level at which we can recognize them as smells. This shows that receptors in the olfactory epithelium are signalling when they detect some smell molecules but this information is used at a pre-conscious level. Smell is affecting behaviour without us being aware of the signalling that is going on. It’s interesting to consider that our noses are doing work behind the scenes, and that as we taste wine, some of our verdicts are potentially being influenced by smells we aren’t aware of.
There’s also the fascinating possibility that at the receptor level, we have an incredibly acute sense of smell, but that a lot of this information is being filtered out at the brain processing level because evolution has decided that it’s simply not useful. Maybe there is a drug out there somewhere that could unlock this information temporarily? It would be amazing to live in a world of heightened smell for a week or two.
And my experience? After a few days of judging intensively, I find that I make decisions quicker and – I think – more accurately. But it would be great to have some data to back this theory up with.