An important underlying assumption behind wine guides, critics' ratings, wine competitions and the notion of which wines are the 'best', is that when we are tasting a wine, we are all experiencing the same thing. However, this assumption has been called into question by the observation that there exist measurable individual differences in the sense of taste. This research, although not new, has gone largely unnoticed by the wine community.

I first became aware of it some years ago when attending a conference on 'The molecular basis of smell and taste transduction', in my professional capacity as a science editor*. At the beginning of her paper, Yale professor Linda Bartoshuk handed out small squares of blotting paper which had been soaked in a chemical, 6-N-propylthiouracil (PROP). At a particular point in her presentation, we were instructed to place this paper on our tongues. Approximately one-quarter of the audience (myself included) could taste nothing. One-half experienced an unpleasant bitter taste. The remainder found the taste repulsively bitter, and immediately had to rush for the bathroom to wash their mouths out.

What we were experiencing was a phenomenon first discovered in 1931, by a researcher called Fox. While synthesizing a chemical relative of PROP, phenylthiocarbamate, some of the chemical blew into the air. He could taste nothing, while his colleague experienced an extreme bitter sensation. It turns out that there are genetic differences in the ability of individuals to taste bitter and hot compounds, with the population breaking down into one-quarter 'supertasters' (with enhanced sensitivity), one-quarter 'non-tasters' (reduced sensitivity), and one-half 'normal tasters'. This differential sensitivity has to do with the density of taste papillae on the tongue: the supertasters, predictably enough, can be shown to have a far higher number of taste papillae than the non-tasters. Bartoshuk and her colleagues have shown that it is not just bitter compounds that are differentially perceived by supertasters and non-tasters, but also dairy products, artificial sweeteners, capsaicin (the active compound in chilli peppers) and ethanol.

How does this relate to wine?
To address the implications of this research for wine tasting, first it is necessary for us to explore further the nature of 'taste'. When we talk about wine 'tasting', we are actually referring to the combination of the senses of taste and smell. Taste is the less information-rich component here (and arguably of lesser importance): from our tongues we get the four basic tastes of sweet, salty, sour and bitter. In contrast, the olfactory receptors in the back of our noses detect many thousands of different volatile compounds or 'odorants'. And as you will know if you have ever tried tasting wine while suffering from a heavy cold, much of the information we receive about a wine comes from the sense of smell. Interestingly, the brain localizes both smell and taste by the sense of touch: that is, if you have a bit of steak on your tongue, the brain takes both the taste sensation and the smell sensation of 'steak' and makes it seem that these are coming from your tongue, even though much of this information is not. Unlike the sense of taste, there is no evidence that there are significant and discrete differences between individuals in their sense of smell. Nevertheless, these genetic differences in the sense of taste are significant enough to affect the perception of a wine to a degree that the assumption that there is a 'universal palate' is fatally flawed. Bear in mind that red wines in particular may contain substantial quantities of tannic compounds, which are bitter in flavour. It is likely that individuals of each of the different taste categories will react very differently to tannic red wines: what is balanced for one will be unbalanced for another. Although white wines do not contain many grape-derived tannins, they may contain tannins from wood fermentation and ageing, or high levels of acids, all of which may be perceived differently by the different taste groups.

Different 'taste worlds'
What this means is that when a group of say 20 people are all tasting the same wine, they will in fact be experiencing different sensations. Of course, we recognize the fact that people have different taste preferences which have their basis in cultural, psychological and experiential factors, but we are talking here about more than just this: beyond these factors, the people are actually in different taste worlds. That is, even if they are all highly trained professional wine tasters going about their job in an objective fashion, and they are 100% successful in their evaluations, they will not concur about the merits of the wines they are assessing: they are experiencing different things. Now factor in the preferences, and the likelihood that even the most professional taster will likely allow at least some of their preferences to affect their judgement, and the whole thing becomes horribly noisy.

The implications
All this creates terrible difficulties for wine competitions, panel tastings, scoring wines and the notion of 'the best' wines. If you convene a tasting panel, it follows from this research that the different judges will acclaim different wines, no matter how experienced these judges are and how little they let their preferences interfere with their objectivity. The result will be a compromise that will probably little reflect the preferences of any one individual. Of course, there will be faulty wines that all will agree on as being faulty, and such panels may be very effective at sorting wines into broad classes of 'quality'. But for finer judgements, the fact that the critics are in different taste worlds will obscure the less marked distinctions. With regard to the practice of awarding numerical scores for wines, the idea that a score is in any way an intrinsic property of the wine is shown here to be false.

Counsel of despair?
Of course, to throw our arms up in the air and declare that because of this genetic taste variation all wine tasting is meaningless, or to adopt an 'anything goes' approach, would be foolish. However, to simply ignore the potential implications -- which are significant -- would be equally daft. From a positive standpoint, this research offers an explanation for something that has puzzled me for a long time: namely, the contradictory and surprising results from wine competitions and panel tastings, and also the fact that my impressions of particular wines can differ so significantly from those of critics and friends whose palates I respect. If there is a take-home message here, it is that we each need to become confident of our own judgement, and if we are going to follow a critic's ratings, at least we should choose one whose preferences correlate with our own. And as for the wine competitions…