GENETIC CLUES TO WINE TASTING?

Science Suggests Half of All People
Have Either Taste Blindness or Hyper-Sensitivity

Rich Cartiere
Editor

Should men not be included as participants in Burgundy tastings? Should women be left off Cabernet Sauvignon judging panels? Should Asians and senior citizens be eliminated from any such contests?

Better yet, should we simply screen all wine judges for the presence of a gene set that appears to control the intensity of bitterness and sweetness in a whole host of common substances-including alcohol?

Provocative questions, even scary in an Orwellian sense, to ask. But scientists, who have been looking at the genetic component of human taste buds since the 1930s, are close to coming up with tentative answers to these kinds of questions. When they finally do, researchers’ responses could shake the foundations of winemaking and undermine the centuries-old tenet, even if we already admit it is somewhat of a silly concept, that all wine has absolute tasting values.

And if what these scientists already suspect is true, you can throw out anywhere from one-half to three-quarters of what anybody says about food and wine pairings—depending on where those “experts’” own taste buds fall in the genetic dice throw. That’s because according to the hints of genetic science, people might want to match their genetic tasting status with others of the same status before taking any flavor advice from them. Finding somebody who likes Cheddar cheese with Cabernet Sauvignon might be the dead giveaway that you’ve found a tasting mate who sees, or in this case, tastes, the world in the same way you do.

Three Separate Worlds of Taste

Rather than a world where all people taste all substances in the same way, science is now showing that we live in at least three different worlds of taste, separated mainly by intensity of that tasting experience. So-called “supertasters” are hyper-sensitive to basic tastes, while regular tasters experience such sensual pleasures in a moderate manner. Still others can be virtually taste blind to the intensity of many bitter, sweet, sour or salty flavors.

“The tongue is hardwired for behavior in ways scientists are only beginning to understand,” said Linda Bartoshuk, a professor of surgery at the Yale University School of Medicine in New Haven, Conn., and co-organizer of a symposium on the genetics of taste in Seattle last month at the annual meeting of the American Association for the Advancement of Science. Bartoshuk suggests this could explain, for example, why some people crave the sweetness of chocolate with a highly tannic Cabernet, but others may detest the combination, the appropriateness of which—perhaps not by genetic coincidence—happens to be one of the wine/food industry’s longest running controversies.

Editor’s Note: The term supertaster is a misnomer when applied to the wine industry, where the ability to taste a broader range of flavors and gauge intensity and depth is a virtual sign of superior ability rather than a handicapped status. For that reason, WBM has changed the term to “hypertaster” for use in the rest of this article, to alleviate prejudices that such tasters are “superior” to regular tasters, when in fact the opposite is true.)

How the science of taste applies to wine is even more controversial than how it applies to other flavorful substances. At the heart of this sub-debate is the insistence by many, including noted wine quality expert Ann Noble of the University of California, Davis, that, “None of this is very relevant for wine tasting. People learn to taste [wine]; they are not born that way.”

Obviously, not all scientific experts agree. “At the very least, what these professional wine industry people need to recognize is that most people never ‘learn’ to taste wine because they’re only occasional drinkers of it, not connoisseurs,” said another researcher at UC-Davis, familiar with the genetic research on taste buds, but insisting on anonymity. “In fact, a question that comes to mind strikes me as downright heresy in wine circles: Is the reason many people don’t ‘like’ wine rooted not in the fact that they haven’t learned yet how to taste it, but in their genetic predisposition for not liking it, or being unable to taste much of it at all?”

The Science To Date

Bartoshuk’s research, and that of numerous other nutritionists and researchers, strongly suggests that the presence—and/or lack of one or both—of two dominant genes plays the key role in how people taste.

These genes control just how many taste buds people have embedded in the tips of their tongues, where these receptors measure mainly for sweetness, sourness, saltiness and just plain bitterness. While some people may have only a few hundred, others may have tens of thousands.

Each taste bud in the front of the tongue feeds information into two types of nerves, according to Bartoshuk. One, the chorda tympani, a branch of the facial nerve, sends taste signals to the brain for processing. The second, the trigeminal nerve, senses pain, temperature and touch.

“This is really critical,” said Bartoshuk. “It tells us that supertasters are superfeelers and superperceivers, at least with their tongues.”

Scientists also have discovered that the tongues of hypertasters are anatomically different from others. Hypertasters have more fungiform papillae, the mushroom-shaped bumps on the tongue found principally at the tip. These also are generally smaller than in regular or the so-called blind tasters. Hypertasters also have a ring of tissue around them that regular tasters don’t have.

‘Hypertasters’

While the exact roles of the genes are unknown, if a person has two of the hypertaster “dominant” genes, he or she is a “hypertaster,” meaning he experiences a high intensity of bitterness, sourness, sweetness or saltiness in some substances. About one-quarter of all people are believed to be hypertasters, with a higher percentage of women and Asians falling into this category.

While hypertasters can have as many as 1,300 taste pores per square centimeter of tongue, nontasters have as few as 11 buds per square centimeter. The average for hypertasters is 425. (If you conduct the self tasting status test on Page 37, a general rule of thumb would be more than 40 fungiform papillae per square centimeter. The relationship in size between fungiform papillae and taste pores is similar to that of sesame seed to a hamburger bun.)

Despite an innate human affinity for sweet foods, hypertasters find sugary foods, but not aspartame, to be sickeningly sweet. Frosting is yucky. Coffee can be too bitter and alcohol too sharp. Hot peppers and ginger produce an unpleasant burn, but pungent foods are liked. Hypertasters often prefer their food tepid. The taste buds of hypertasters also are “tuned off” to fatty substances, not because of the flavor—which they do not detect—but because of a tactile sensation the brain interprets as viscous, slippery or greasy, said Valerie Duffy, a registered dietitian at the University of Connecticut in Storrs who has co-authored much of the research in this area with Bartoshuk.

Oddly, hypertasters tend not to like the strong tastes of many fruits and vegetables, according to research by Adam Drewnoski, a professor of public health psychology and psychiatry at the University of Michigan in Ann Arbor. Drewnowski suggests this may be due to the presence of flavonoids and several cancer-preventing agents, many of which also are found in wine, which itself has so many organic chemical compounds it is considered more complex than blood serum. Hypertasters typically do not like grapefuit juice or even orange juice, which also are high in such substances.

When it comes to wine, hypertasters might be in the worst of all positions for wine judging. They would not like the heavy tannins of many wines. They would be more sensitive than anyone else to off-dry wines and might find sweet wines and heavy alcohol wines repulsive. The softer flavors of Burgundy may be more to their liking than Cabernet Sauvignon or the spiciness of Chianti or Zinfandel.

Researchers privately have joked that hypertasters might even prefer the industrial winemaking process, with its heavy fining and racking procedures which have long been known for stripping out flavonoids and the other chemical compounds that make up the unique tastes of wines.

Complicating the picture, there are cultural influences that may affect the preferences of the different tasters. Women hypertasters, for example, intensely disliked anything that smacked of sweetness, while hypertasting men tended to appreciate the sweetness more. Researchers suspect this may be due to cultural influences that teach women that fatty and sweet foods are more fattening and women then associate greater sensitivity to that issue than men. Men and women hypertasters do not have anatomical differences in their tastebuds.

‘Regular Tasters’

If a person has just one of the two hypertaster genes, with one dominant and one recessive, they are classified as “regular tasters.” About half of all people are believed to be in this category. The average number of taste pores per square centimeter is 184, half those of hypertasters. (In the self test, regular tasters will have about 20-40 of the fungiform papillae.)

Because of the random nature of genetic makeups, it would be very common for parents who are both regular tasters—one hypertaster gene each—to have children who would fit into either the hypertaster—two hypertaster genes—or non-taster—no hypertaster genes at all—categories.

“The world is built for regular tasters, said Bartoshuk, noting that such people experience foods as not too sweet, bitter, salty or sour.

When it comes to wine, regular tasters would choose middle-of-the-road flavors, finding sugars more palatable, heavy alcohol less bitter and tannins less biting than hypertasters.

‘Non-Tasters’

So-called “non-tasters” have neither of the hypertaster dominant genes, but two of the recessive genes. As a result, they have far fewer tastebuds on the tongue tip and thus have a sort of “taste blindness.” About a quarter of all people fall into this category. The average number of taste pores per square centimeter is 96, half that of regular tasters and barely one-fourth of hypertasters. (On the self test, expect under 20 fungiform papillae.) Non-tasters simply don’t experience the intensity of foods that others do.

In wines, non-tasters may not mind tannins, would be less sensitive to the sweetness of off-dry wines, would find little bitterness in more heavily alcoholic drinks and might prefer more spicy foods because they would be searching for some semblance of intense taste. They also would be prone to finding sweet wines more acceptable.

Non-tasting also may occur more frequently in old age, for reasons not entirely understood, although perhaps linked to hormone production, and in more men than women.

Bartoshuk herself is a non-taster, and as such has a practice that should be a real eye-opener to just about any wine marketer: she adds sugar to her wine to allow her to taste a little sweetness in it.

How it All Got Started

Genetic tasting research has been concentrated on the same substance since 1931, when Arthur L. Fox, a chemist at the DuPont Co., synthesized a called phylthiocarbamide. As Bartoshuk tells the story, after some of the PTC exploded into the air, a colleague commented on how bitter it was, yet Fox said he tasted nothing. Intrigued, Fox handed out crystals of PTC at the 1932 AAAS meeting, asking how many passers-by could taste it. About a quarter of the people were non-tasters, while everyone else said PTC was bitter.

Geneticists and anthropologists at the time were fascinated, and they quickly discovered the presence of the genes. At the time, they classified people as non-tasters and as tasters. Bartoshuk’s role in the development of the science was to recognize that there was a third level of tasters, determined by the presence of one of the genes.

Genetic tasting research today is carried out with another substance, 6-n-proplthiouracil, or PROP, which is used to treat Grave’s Disease, known as hyperthyroidism. Again, some find it intensely bitter while others cannot taste it at all. Since neither PTC nor PROP is found in everyday food or beverages, Bartoshuk and her colleagues have furthered the field by examining substances with tasting qualities that correlate to PROP. The modern-day challenge, according to Bartoshuk’s colleagues, is to “explore the tasting realm of possibilities.”

Alcohol, Cheddar Cheese

While the wine tasting scenarios presented above are clearly speculation, and in fact the opposite may turn out to be true under the light of scientific exploration, Bartoshuk and colleagues already have found numerous correlations between people’s abilities to taste PROP/PTC and food and drinks.

The experiment with the greatest relevance to the wine industry involved ethyl alcohol, conducted by Bartoshuk and eight other researchers in 1993. PROP hypertasters and regular tasters tasted concentrations of ethyl alcohol as more bitter and more “irritating” on the tips of their tongues. As well, when a series of ethyl alcohol concentrates (10-50 percent, i.e. equivalent to 5 to 25 percent alcohol concentration in beverages) were tested with the whole mouth, with a sip and spit method, hypertasters and regular tasters also perceived more bitterness than nontasters did for all concentrations.

Bartoshuk and colleagues hypothesized that hypertasters and regular tasters were “protected” from alcoholism to a degree because the alcohol was “less palatable” to them than to nontasters. They were supported by other recent research by two other members of the research team showing that children of alcoholics include a higher proportion of non-tasters than nonalcoholic children of nonalcoholics.

In another study Bartoshuk study, non-taster children liked the sharpness of cheddar cheese more than taster children. Hypertasters in this study received the greatest “burn” from chili peppers (active ingredient capsaicin).

In another study, Bartoshuk and colleagues discovered an unexpected result—that tasters who were better able to taste the bitterness of PROP also were more interested in cooking and “food interest and eating enjoyment… and several primary taste quality food items.” The study also found that PROP tasters had less chronic diseases, less body fat and less body weight, leading them to suspect that hypertasters and regular tasters may have a health advantage over those blind to such tastes.

(Some of the material in this story is drawn with permission from a New York Times report on the Seattle conference)