The World of Fine Wine
Have you ever wondered why you are able to smell or taste something that your drinking or tasting companion cannot grasp? Dr Jamie Goode might have the answer—a specific anosmia or a specific aguesia—whose recent recognition suggests that there can be no “single truth” about a wine.
Rotundone is the name given to a rather interesting wine flavor compound. Discovered by scientists at the Australian Wine Research Institute (AWRI) in 2007, it is the molecule responsible for the “black pepper” aroma in some wines made with the Shiraz/Syrah grape variety.1 Technically speaking, rotundone is a bicyclic sequiterpene, and as well as making wine taste peppery, it is also responsible for similar aromas and flavors in herbs and spices, including peppercorns. It’s incredibly powerful, too, being detectable even at tiny concentrations.
The reason I mention it here is that one of its most remarkable properties is that one fifth of people can’t smell it at all. Think of the implications of this. The AWRI study showed that while most people detect rotundone at the miniscule concentration of 8 nanograms per liter (ng/l) in water, 20 percent of the panelists they used for sensory analysis failed to detect it at 4,000ng/l. This sort of smell “blindness” is known as a specific anosmia.
While many such anosmias have been identified, it wasn’t until 2007 that the first study was published linking an anosmia with a specific mutation in an olfactory receptor gene in humans.2 This study began with the precept that people’s perceptual variations of certain odors, as well as their assessments of the pleasantness or otherwise of these odors, differ markedly. As an example, a steroid called androstenone is variously perceived by different individuals as offensive (“sweaty, urinous”), pleasant (“sweet, floral”), or simply as odorless. The authors combined a psychophysical study of a large group of people—that is, one in which they look at the perception of a range of odors—with a genetic study in which they looked at how these individuals differed in the expression of the genes encoding 335 putative human olfactory receptors. They demonstrated that a human odorant receptor, OR7D4, is activated in test-tube experiments by androstenone, and then they showed that there were genetic differences among humans in this receptor, which could account for their different responses to this odorant. It is likely that similar genetic differences also occur for other odorant receptors.
It is not surprising that anosmias should exist. While we each have a suite of a few thousand different olfactory receptors (which are transmembrane proteins; each olfactory epithelial cell has just one type), we can discriminate many more different aroma molecules (known as odorants).
In fact, the precise details of how we “smell” are, at a molecular level, still mysterious. The two competing theories are proposing rather different mechanisms. The orthodox view is that olfactory receptors recognize shapes of molecules. This seems logical and fits with many results, but there are anomalies that have led others to propose quite a different mechanism. For example, two molecules of almost exactly the same molecular shape can smell quite different. The alternative theory of smell was devised by a researcher called Luca Turin, who is the thorn in the olfaction research community’s side. His theory is that the olfactory receptors detect not the shape but the vibrational properties of odorant molecules.
Irrespective of who is right, the existence of specific anosmias, especially when these involve wine flavor compounds such as rotundone, is of great relevance to the practice of wine tasting and criticism. Here we have a compound that is responsible for the pepperiness that is such a valued character of many Shiraz/Syrah-based wines, and 20 percent of tasters just don’t get it. Imagine there are two judges at a wine show, one of whom just doesn’t get rotundone and one who does. What to one judge may be a beautifully peppery Shiraz might be quite a different wine to the other.
There are similarly striking findings from research on taste. It seems
that when it comes to detecting bitterness in particular, tasters vary wildly in their performance. The well-publicized work by Linda Bartoshuk and colleagues on PROP tasters and non-tasters is the most graphic illustration of this. PROP (propylthiouracil) is a compound that some people find extremely bitter, while others are unable to taste it at all (this is known as a specific aguesia). As well as falling into taster or non-taster groups, there is a third population that is exquisitely sensitive to the bitterness of PROP. These people are known as “super-” or “hyper-” tasters. As well as being highly sensitive to PROP, this third population—around one quarter of people tested—are also sensitive to the burn of chili pepper and other extreme flavors. Bartoshuk describes them as living in a “neon” taste world. They have a superabundance of fungiform papillae (the structures housing taste buds) on their tongues.
In complete agreement with these observations on individual differences are the experiences of companies that use large consumer sensory panels. Jane Robichaud works for US company Tragon, and her role is to use these panels to help producers tune their wines to consumer preferences, by uncovering the drivers of these preferences. As such, Robichaud has much experience in assessing people’s sensory perceptions of wine. Robichaud is a trained winemaker, as well as a sensory scientist, and was one of the authors of the celebrated wine aroma wheel; she worked for Beringer before moving to Tragon. Much of her current work involves using a process known as product optimization, which consists of quantitative consumer sensory research that then provides winemakers with practical information that can help them make “consumer-defined” wines. They recruit members of the public and put them through a two-day sensory analysis boot camp. “They don’t need to be connoisseurs, but they need to be regular consumers who are good at group dynamics,” says Robichaud. Typically, 70 percent of these people will pass, and 30 percent will have to drop out. The job of this trained panel is to come up with the descriptive language that will be used to describe the wines being examined. The second stage is known as the optimization phase. For this, typically 150 to 200 or more of the “target” consumers are recruited. “Interestingly, we find that people are wired quite differently, such that they like different things,” says Robichaud. “Taking coffee as an example, some people like it strong, dark, and rich; some like it medium and coffee-ish; and some like brown water.” Robichaud explains that it is possible to find discrete “preference segments” (defined as groups of consumers exhibiting similar and distinct likes for specific combinations of attributes). “About 30 percent of the population are not good measuring devices,” concludes Robichaud. This seems to tally well with the work on PROP sensitivities, but Robichaud doesn’t think that PROP status is all that useful a measure. “We did a bit of PROP testing at Beringer, and it didn’t work very well: It bore no relation to who was a good bitterness taster.” The problem here seems to be that there are so many chemical compounds that elicit bitter tastes, with quite different structures, and PROP is just one of them. Robichaud does, however, think that about one third of people don’t seem to
get bitterness in wines at all.
Information and perception
There are important implications of observations such as these for
wine tasting. It seems that we may be living in rather different worlds as wine tasters and that however much we try to iron out differences in preference or variation in critics’ appraisals, some of this could have its basis in biology. All this is, of course, to do with different perceptions relying on the data-gathering apparatus of the taste buds and olfactory receptors. There is a lot more to wine tasting than mere measurement of chemical entities present in the wine, as a number of scientific studies on the way the brain processes this sort of information have shown.
Perhaps the most interesting of these is the relatively recent study by a group of researchers from California working in the new field of neuroeconomics. They used a technique called functional magnetic resonance imaging (fMRI) to show that the information people are given about the wine can change their actual perception of the wine and how pleasant they find it.3 The authors discuss an economics term called experienced utility (EU) and describe how marketing efforts frequently attempt to change the EU of a particular good, without changing the nature of the good. The researchers chose to use wine as a test case of how price can modify EU. They fed a group of 20 subjects five different Cabernet Sauvignon wines while they were in an MRI machine. The subjects were told the retail prices of the wines they were tasting and were told to focus on the flavor of the wine and say how much they liked them. There was, however, a clever twist to this experiment: In reality, only three wines were being presented to the subjects, with two of the wines being presented as different wines at different price points. So, the five different wines the subjects tasted were: $5 wine (wine 1, its real price); $10 wine (wine 2, which was actually a $90 wine); $35 wine (wine 3); $45 wine (wine 1, at a fake price) and $90 wine (wine 2 at its real price).
Unsurprisingly, there was a correlation between price and liking. Significantly, subjects preferred wines 1 and 2 when they were told they were drinking the higher-priced wines. The brain scans, comparing the response of subjects when tasting the same wines but believing them to be differently priced, showed that the parts of the brain that experience pleasure are more active when subjects think the wine is of a higher price. The price isn’t just affecting perceived quality—it seems to be affecting the actual quality of the wine by changing the nature of the perceptive experience. The importance of these results are that they show that our expectation as we approach wine—perhaps caused by sight of the label—will actually change the nature of our wine-drinking experience.
No “single truth”
What does all this mean? Is the current practice of wine tasting fatally flawed? Not at all. Indeed, it’s remarkable, given this sort of insight, that we all agree as much as we do on what makes a great wine. But I would argue for a more grown-up view on wine tasting that takes this sort of variation into account, compared with the current simplified version that views the taste of the wine simply as a property of a wine that we can all “get” in the same way if we are skilled enough tasters.
In practice, for the student of fine wines these observations mean that there is no “single truth” about a wine. While much of the quality of fine wine can only be appreciated by experience and learning—a realm that is accessible to almost all—the existence of specific anosmias and aguesias means that, at the most basic level, the same wine is not the same to all people. We do indeed live in different taste worlds.
Stating this another way, there is a level at which wine preference is learned, and we can learn to love flavors that initially we find quite difficult. But there is also a level at which aesthetic decisions on style and balance will be affected by our biological differences. It means that there is little room for a strictly dogmatic approach to wine quality. While we may all be in broad general agreement, it is over the fine distinctions—so important in wine appreciation—that we will find ourselves disagreeing.
This isn’t the whole story. Perhaps the main reason tasters disagree isn’t biology, but competence. My limited experience in wine judging has convinced me that some people in the trade are simply better tasters than others. Some seem to have inconsistent palates (how good would they be at picking out duplicated wines in a large flight?), and others seem to have bizarre preferences (meaning their stylistic judgment is questionable).
The existence of varying taste worlds is one of the reasons why I really like the tasting policy of The World of Fine Wine, which seems to rest on a sound theoretical basis, taking into account real individual differences. Time and time again, we see one experienced taster award a wine, say, 17 points, and another award the same wine 11 points. Great wines are often divisive. Knowing the identity of the taster and reading their comments, I can choose to follow the one whose palate I find myself aligned with. If scores are averaged or a consensus is reached, then the various differences among the tasters act as noise in the system and the data are compromised to a degree. This may be fine for judging commercial wines in a large competition, but I’d argue that it doesn’t really work for the finest, most interesting wines.
1. M Parker, AP Pollnitz, D Cozzolino, IL Francis, MJ Herderich, “Identification and quantification of a marker compound for ‘pepper’ aroma and flavor in Shiraz grape berries by combination of chemometrics and gas chromatography-mass spectrometry,” Journal of Agricultural and Food Chemistry 55 (2007), pp.5948–55. C Wood, TE Siebert, M Parker, DL Capone, GM Elsey, AP Pollnitz, M Eggers, M Meier, T Vössing, S Widder, G Krammer, MA Sefton, MJ Herderich, “From wine to pepper: rotundone, an obscure sesquiterpene, is a potent spicy aroma compound,” Journal of Agricultural and Food Chemistry 56 (2008), pp.3738–44. TE Siebert, C Wood, GM Elsey, AP Pollnitz, “Determination of Rotundone, the Pepper Aroma Impact Compound, in Grapes and Wine,” Journal of Agricultural and Food Chemistry 56 (2008), pp.3745–48.
2. A Keller, H Zhuang, Q Chi, LB Vosshall, H Matsunami, “Genetic variation in a human odorant receptor alters odour perception,” Nature 449 (2007), pp.468–72.
3. H Plassmann, J O’Doherty, B Shiv, A Rangel, “Marketing actions can modulate neural representations of experienced pleasantness,” Proceedings of the National Academy of Sciences of the United States of America 105 (2008), pp.1050–54.
This article originally appeared in Issue 25, 2009 of The World of Fine Wine magazine, a quarterly magazine devoted to wine and all thing vinous.
It boasts an authoritative cast of writers—including Huon Hooke, Andrew Caillard MW, James Halliday, David Schildknecht, Jancis Robinson MW, and Oz Clarke—contributing some of the most original writing published today, under the editorial baton of Neil Beckett. Find out more at the magazine website: www.finewinemag.com
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