To answer this question, Pete Wells explores the geeky world of sensory science—and learns taste is as much in the mind as the mouth.
Subject A sits in a white booth. The booth is dark except for the fake-fireplace glow cast by a dim red lamp and the orange monitor screen that is now telling Subject A what to do.
Please begin by using one piece of bread to absorb all of the salad dressing. Put the bread in your mouth, thoroughly chew, and then either swallow or spit the remains. It is imperative that you be consistent in this action for the duration of the tastings.
Immediately smell the wine once or twice to rate all aroma intensities. Quickly move to tasting the wine. Cover the whole area of the mouth with the wine, and then spit. Rate all of the flavor attributes immediately after only one taste, trusting your first impression.
A panel slides open and a hand appears, holding a glass of straw-colored liquid. The glass is labeled "604." Subject A places Liquid 604 in her mouth and expectorates a few seconds later. The monitor screen reads AROMA and shows four horizontal bars labeled LOW on the left and HIGH on the right. Sliding a mouse, Subject A moves a cursor across the bars marked with four flavor categories: FLORAL, OAK, BUTTER and CANNED CORN.
The process repeats until Subject A has tasted six wines in every possible combination with 20 different dressings. A battery of statistical programs will swirl her responses together with those of 10 other subjects. Finally the computers will deliver a series of charts that demonstrate whether or not wine is enhanced by food.
I was inside a sensory-science lab at the University of California, Davis, when I observed Subject A. Davis has two such labs; this one is in the Department of Viticulture & Enology, which has taught more winemakers and vintners than any other place in the country. One V&E researcher has been looking for a new way to tell, through chemical analysis, when grapes are at their most flavorful. Another came up with a device that detects rot in a cartful of grapes; it works just like a pregnancy test. A third is an expert on a vineyard malady known as berry shrivel. Most of them study how wine is made. Hildegarde Heymann, the professor who runs the sensory-science lab, wants to know how it tastes.
Sensory science dates back to the Second World War when American G.I.s were dumping their K-rations by the ton, untouched. Even the most nutritious meal won't fortify soldiers who refuse to eat it, and so the army called in scientists and psychologists to make the rations taste better. Using the scientific method, these experts utilized a reliable, standardized method of teaching people to break down the sensory experience of eating into its components—starting with taste, aroma and texture, and getting more specific from there. Each component could then be scored for its relative intensity. Panelists who were taught this "descriptive analysis" technique turned out to be extremely reliable. A wine critic might score a bottle of Côte-Rôtie one way on Monday and another on Tuesday, but trained panelists sitting in sensory booths delivered the same rankings day after day.
Today, many fast-food chains rely on descriptive analysis when they are launching, say, a new chicken sandwich. McCormick, the spice company, has an entire sensory-science center working on its "flavor systems," a billion-dollar-a-year business devoted to ginning up new additives and ingredients. Sensory scientists at Coca-Cola have studied perceptions and preferences around the world; they probably could (but definitely won't) tell you whether Germans and Mexicans experienced the taste of caramel differently.
This soulless, numerical approach may yield an acceptable McNugget, but should it be let loose on a delicate and lyrical Pinot Noir? In fact, it already has. Many oenophiles might feel a bit queasy if they knew just how widely sensory science is applied in the wine world. Hogue Cellars used it to test its screw caps. A corporation called Nomacorc relied on it to eliminate stray odors from its synthetic corks, which can now be found inside the necks of over a billion bottles a year. The big wine conglomerates have hired their own sensory scientists; Jane Robichaud, a graduate of the Davis sensory program, has trained the employees of Beringer Blass Wine Estates in California in descriptive analysis, enlisting them in studies on how long a superstore can stock a Chardonnay under bright lights without hurting the wine. Robichaud helped Beringer fine-tune the blend in its popular Stone Cellars line; E&J Gallo did similar research when it took Red Bicyclette out for a test drive.
Some people feel that wine is the product of its terroir—the dirt, the rain, the slant of a hillside. Or they may hand the credit to a winemaker who is half artisan, half poet. Either way, sensory science probably makes them a little uneasy because it seems to squeeze the artistry out of wine. It cuts out the human factor. Even if we've made our peace with modern tools like reverse osmosis and micro-oxygenation, the very notion that a winery would borrow methods from Burger King conjures up a nightmare of white-coated technicians in some Napa Valley version of Mission Control, tweaking knobs and studying data as rivers of Merlot gush from a pipeline.
But the dark arts of sensory science are invoked at the elite end of the winemaking spectrum, too, where inky drops of Cabernet accrete in bottles that have been pre-sold to avid collectors. As an undergraduate, blue-chip winemaker Mia Klein studied with Ann C. Noble, Heymann's predecessor. (Noble is famous for inventing the Wine Aroma Wheel, a chart that helps drinkers write more objective tasting notes by naming every smell commonly found in a glass of wine—from wet dog to apricot.) Klein has drawn on sensory science's methodical approach, if not its exact techniques, to craft better wines for her own Selene Wines label and for such high-end properties as Dalla Valle. She recently began asking her consulting clients to come up with two blends and then write down their impressions to "see what each component of the blend brings to the wine that we like, and what it brings that we don't like. I haven't met anybody yet who doesn't really enjoy that," she says. Klein believes winemaking can be an art. Still, she says, "It can be useful to have that discipline behind you. It animates the art side of things, if you use it appropriately."
Heymann is sympathetic to the needs of winemakers. Raised in South Africa, she worked at the Stellenbosch Farmers Winery before getting her PhD—although, she says, "I would have been an absolutely horrible winemaker. I don't take risks." At Davis, she was a star student, but for a time she was better known for her smell than her scholarship. As part of her dissertation, she was examining the sensory effects of the compound responsible for the aroma of green bell peppers, which also turns up in Cabernet Sauvignon. To conduct her experiments, she dissolved the compound in water and bottled the solutions. The trouble was that the solutions would get weaker and weaker, ruining her study. She wondered if light was destroying the compound, but science told her that was impossible: The molecular structure was wrong for a light-sensitive chemical.
The compound, 2-methoxy-3-isobutylpyrazine, is one of the most powerful odorants on earth. Place two drops in a swimming pool and you might as well go for a dip in a vat of pepper juice. It soaked into Heymann's clothes; it soaked into her skin. Once she slipped quietly into Noble's class a few minutes late. Noble sniffed the air and, without turning around from the blackboard, announced that Hildegarde Heymann had entered the room. Heymann contemplated her future: constantly refilling little glass vials; constantly smelling like bell peppers; never finishing her dissertation. She was walking across campus one day, crying with frustration, and as her tears refracted the California sunshine she thought, It must be the light. She ran some tests. What science had told her was wrong. Light destroys 2-methoxy-3-isobutylpyrazine.
I hate green bell peppers with a hate beyond mere hatred. The tale of Heymann's dissertation is, to me, a horror story. But to winemakers in fog-drenched Monterey, it was huge news. Monterey County was producing lots of Cabernet at the time, and much of it reeked of green pepper. (Shudder, retch.) Now winemakers knew why. In response to Heymann's findings, they either began ripping out their Cabernet vines or pruning them so more sunlight hit the grapes.
Doctorate in hand at last, Heymann went on to write a slew of papers with excellent titles like "Physical and Sensory Characteristics of Cat Litter" and "Time-Intensity Evaluation of Oral Burn." She co-authored a sensory-science textbook as well as a study on cheese, from which I learned about the "creep/recovery test" as well as a machine called the B.I.T.E. Master, which chews just like a set of human teeth. Most fascinating of all, though, were her studies on whether food positively or negatively affects the taste of wine. This may sound like a joke—a jab at the cluelessness of the academy. Everybody knows that wine and food enhance one another, right? But things that everybody knows sometimes turn out to be wrong.
Heymann showed me a stack of published papers, most of which she helped write, in which panelists trained in descriptive analysis tasted food and wine in quick succession and then rated the intensity of the flavors in the wine. Time and again, these flavors were less intense when the wine was paired with food than when it was sampled on its own. When the subjects in one of Heymann's experiments ate a cube of Gruyère and then sipped a Merlot, the wine came across as a little less oaky, a little less fruity. Still stranger, for people who are used to thinking that each food goes best with just one or two varietals, Heymann learned every cheese she tested had the same dampening effect on every wine in the study—Syrah, Cabernet Sauvignon, Pinot Noir, whatever.
In other words, if you're worried about finding the bottle that will best complement the raw-milk Pecorino you're serving tomorrow night, the answer provided by sensory science is: Stop fretting. They're all equally good. Or, if you tend to look at the dark side, equally bad.
Heymann isn't saying that wine and food don't go together; after all, she and her husband open a bottle before dinner every night. She's just saying that we should be deeply skeptical when an expert decrees that roast lamb "demands" a wine from the Côte d'Or. "The problem with starting to make rules is that they are not one-size-fits-all," Heymann explains. "I may find that one wine goes better with a certain food, but somebody else may choose a different wine. There's definitely an idiosyncrasy to the choice." She says that the consumer "take-away" from her research is to forget about finding ideal wine-food pairs and instead "drink the wines you love with the food you love."
Fine advice. Still, I kept wondering if Heymann was looking through the wrong end of the microscope—because if I'm sure of anything, it's that some port and a pile of blue cheese end a meal with a bang. But when I sit down in the office that Heymann has decorated with pictures of cats, she begins to explain that the two-step port does with Stilton might be something you can't capture in a sensory booth.
To make her point, she shows me another paper, which she calls "the rinse study." Panelists were told that the purpose of the study was to discover which grape varietal cleansed the palate most efficiently. They were asked to score butter, sour cream and yogurt after a sip of wine. The wines did change the taste of the food, the subjects reported—but not by much. And the data was nice and neat—Chardonnay had the same impact on yogurt as it did on butter. Then Heymann ran the same protocol with the same foods, the same wines and the same panelists—only this time, she told them that it was a food-and-wine pairing study. Suddenly, she says, "all hell broke loose." The panelists tasted all kinds of things that hadn't been there before, and the differences they had noted before struck them as more intense this time. When Heymann plotted the data it looked like a trigger-happy gunman had sprayed the charts with buckshot. The only difference between the studies was the panelists' belief about the purpose of the experiment. "It's not happening in the mouth," Heymann said. "I think it's happening in here." She pointed to her temple.
Sensory science has bumped into this kind of thing before. Tell someone you're giving them a glass of pineapple juice and they'll taste pineapple, even if it's orange. That's what scientists call a cognitive effect. Back in the 1980s, Coca-Cola spent vast sums proving that in blind taste tests, people liked the new Coke more than the classic formula. Then they put it on the market and everybody hated it. The company had ignored loyalty to the old Coke. Cognitive.
Another case in point is Heymann's abiding fondness for a sticky, red, fizzy wine called Ballatore. "It's probably the most disgusting thing I could have chosen as a favorite wine," she says. "It's terrible, it's sickeningly sweet, it has fake bubbles. But every time I drink it I'm reminded of Easter Sunday 1986." Heymann had been invited to a lunch in Napa Valley. No expense was spared. Château Pétrus was poured. Then, with the fruit tart, the hostess uncorked Ballatore, Gallo's Asti Spumante knockoff, which sells for about $7 a bottle. "With no explanation, no excuses," Heymann recalls. "And that impressed me. If you gave it to me in a sensory booth I could tell you what's wrong with it, and there's a long list. But it's my favorite wine because it evokes that memory."
You could look at those stories and decide that we're all delusional—scientists and fans of classic Coke alike. Or you could say that thinking plays an integral part in drinking. You're not born loving or hating Riesling—you have to learn. And learned flavors often drag a bundle of emotional or intellectual associations along behind them. If we encounter a new food that's sweet and high in calories, we'll learn to like its aroma. We'll also learn to like a smell if we're happy when we encounter it. (There—all of Proust in one sentence.) But if something makes us ill, we'll hate its aroma. I'm always meeting people who can't stand tequila because once long ago they downed six margaritas more than were strictly necessary.
Yes, we pay attention to the reports being fired off from our tongues and our noses when we eat. But as that news bolts through the brain, it meets up with our memories, our beliefs, our ideas. Sensory science can teach us a lot about what happens in our mouths. But if Heymann's theories about food and wine pairing turn out to be right, they will reveal something just as interesting: Science will show us where our mouths stop and our minds take over.
Comments? E-mail Pete Wells at firstname.lastname@example.org
Pete Wells is a contributing editor to Food & Wine.