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Robo-Tongues Taste for Better Wine

by
Scope Correspondent

Sommeliers beware; a robot “tongue” is being trained to taste wine.

The electronic tongue—a machine that “tastes”—has been used to study the qualities of wine, water, beer, and even urine, but a team at Washington State University is working on further developing the machine’s wine-tasting skills in a large-scale red wine analysis project. The researchers arecurrently analyzing sixty-one different commercial merlots, local Washington vintages of varying price levels, to understand the characteristics that shape a good wine.

Although wine has been sniffed, swirled, and sipped for centuries, the chemicals and compounds that make up wine’s complex features remain unidentified. Using built-in chemical sensors, the e-tongue can perceive taste qualities in a fashion similar to the human tongue, yet with no boundaries of time, palatability, or toxicity—and with the added ability to detect specific molecules.

According to sensory scientists, a human’s 10,000 taste buds detect five basic taste qualities—sweet, salty, sour, bitter, and umami—as well as two newly recognized qualities, calcium and fat. The e-tongue at Washington State has seven artificial sensors, which detect the five basic qualities, along with metallic and spicy. The $90,000 e-tongue looks nothing like a real tongue. The “tongue” is a set of tubes bound together, each of which has an artificial sensor on its tip.

To prepare the robot’s wine tasting, scientists line up several beakers of wine samples on a rotating wheel called an autosampler. To “taste” a sample, the tongue dips into a beaker, then into water to cleanse its palate, and so on.

The e-tongue’s sensors work by measuring voltages in samples, like the electronic signals sent from the tongue to the brain. The results show up as numbers on a computer screen, which represent the taste qualities present in the sample.

Charles Diako, a Ph.D. student and super-taster who works with the e-tongue, compared the machine parts to those of the human body: “You have the tongue, with the sensors or taste buds, and you have the brain, which is the analyzer, and you have the recognition system, the responses, which are displayed on the monitor.”

The ultimate goal is to identify the specific compounds responsible for the hints of oak, the earthiness, and the flashes of gooseberry that color the descriptions of wine tasters. “Eventually what we’d like to do is find out what [the sensors are] reacting to, and how whatever’s in the wine…influences how we perceive it,” said Carolyn Ross, assistant professor of food science and manager of the WSU Sensory Evaluation Unit.

Once specific compounds behind taste are pinpointed, the e-tongue can then be trained to detect and respond to these compounds. “It’s a mystery right now,” said Ross, but “I know where we would start looking.”

Purchasing the machine in September 2012, Washington State University became one of the few academic institutions to own an electronic tongue. Behind California, Washington is the second biggest wine producer in the U.S. A few Washington wine companies have expressed interest in this device to inform their own winemaking.

Using e-tongue data, the researchers have already grouped the sixty-one wines into six different categories based on dominant taste profiles, including sweet, bitter, and metallic. The next step is to compare these results with human assessment.

To acquire the human portion of this research, Diako recruited college students for a six-week-long wine tasting training program. The thirteen trained students formed a sensory panel to evaluate the sixty-one merlots of interest. This sensory evaluation was completed in November 2013. The panel rated wine qualities, such as sweetness, on a number scale from 0 to 15. “It’s hard to get people to agree [on a rating],” Diako noted.

Typical wine analysis involves a trained sensory panel, but recent research has questioned the abilities of even seasoned wine tasters to judge wine with any consistency. Besides natural human taste differences, a number of studies have also shown an arbitrary effect of price on a person’s wine ranking, with expensive wine rating higher than the same wine with a cheaper price tag.

Robert Hodgson, owner of a winery in California who has studied the consistency in judging at wine competitions, believes that “the results of wine competitions are unreliable in terms of predicting wine quality.” “There’s an awful lot of psychology that goes into the evaluation of wines,” he said. “I know that my own appreciation of wine varies based on my body chemistry, whether I’ve had an argument with my wife, etc.”

“The one thing you and I know about human beings is that they’re so variable,” said Diako. “[The electric tongue] brings objectivity into wine sensory analysis.” And, Diako added, “the machine doesn’t know the price.”

Also, unlike like a human sommelier, the electronic tongue never gets tired. “We do a lot of sensory evaluation, and we find that fatigue is a big thing…people can only evaluate so many samples,” said Ross. But “the electronic tongue would never replace a person…just maybe reduce the number of samples they’d need to evaluate,” Ross said.

Besides red wine analysis, the Washington State team has successfully used the tongue to examine artificial sweeteners used in granola bars and the bubbliness in sparkling wine. “There are a lot of things you can do with that machine,” Diako said, “we’re now just scratching the surface.”

Can a machine really assess the quality of a wine? Yes, said Diako, as long as you can give it a set of criteria for what constitutes exceptional wine. “It’s all a quest to get better wine, and to understand more what goes into making a good wine,” Diako said.

Yet with the variability in human perceptions and opinions, it seems there is no quantifying or replacing the human aspect of wine tasting. “What really makes a good wine is dependent on what you like and your taste buds,” Diako said.

Despite his intensive wine research and super-tasting abilities, for Diako, “what makes a good wine is location and the mood.”

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