Scientists at the University of Glasgow in Scotland have developed an artificial tongue capable of distinguishing between different brands of whisky, a potentially useful tool to combat counterfeit whiskeys on the international market. The researchers describe their device in a new paper in Nanoscale.

There is an exploding demand for expensive rare whiskies, so naturally there has been a corresponding increase in the number of counterfeit bottles infiltrating the market. A study last year subjected 55 randomly selected bottles from auctions, private collectors, and retailers to radiocarbon dating and found that 21 of them were either outright fakes or not distilled in the year claimed on the label.

Ten of those fakes were supposed to be single-malt scotches from 1900 or earlier, prompting Rare Whisky 101 cofounder David Robertson to publicly declare, "It is our genuine belief that every purported pre-1900 bottle should be assumed fake until proven genuine, certainly if the bottle claims to be a single malt Scotch whisky." There's also an influx of counterfeit cheaper whiskies seeping into the markets, which could pose an even greater challenge, albeit less of a headline-grabbing one.

Clark's lab is primarily focused on building nanoscale metals for biodetection and imaging, but the idea of making an artificial tongue for such a unique application appealed to him. What's unique about his design is that it combines two different kinds of metals: gold and aluminum. Typically, there would be a gold "taste bud" in one location of an artificial tongue and an aluminum one in another spot. Each is chemically modified and then monitored to see how the nanometals' interactions with light change in response to contact with a liquid.

Clark et al. decided to place those two taste buds right next to each other, arranged in a checkerboard pattern, and discovered this allowed them to further shrink the size of this already-tiny device. Having two taste buds on the artificial tongue also gave them two distinct optical profiles of three different whiskies used in their experiments (Glenfiddich, Glen Marnoch, and Laphroaig), while still making just one measurement. "We can make half as many measurements and get the same amount of information," he said.

University of Glasgow

Clark et al.

University of Glasgow

The researchers' artificial tongue isn't looking for a specific kind of chemical; that's what makes it a tongue as opposed to a sensor. Human tongues can distinguish between black coffee and apple juice, for instance, not because we sense particular chemicals in each but because over time we have learned to associate a certain flavor profile with each. That's essentially what Clark's artificial tongue is doing.

"It's analogous to taste in that we are building up a statistical profile of the chemical mixture within that liquid," said Clark. "We're doing that by shining a light on these little taste buds and monitoring how the color of those taste buds changes depending on what whisky is on top of them. Then we run it through a complex algorithm that essentially gives us a flavor profile of it."

"Human beings are set up to be manipulated," said Clark. "Also, flavor is affected by your mood. It's affected by atmosphere—all the psychological aspects of the tasting experience. We are not reliable, so having some sort of cold, calculated machine to give you a statistical breakdown is more accurate and repeatable."

The whisky manufacturers seem to agree. "We really, as an industry, would welcome something which would help to stamp out the counterfeit whisky," Annabel Meikle, director of the Keepers of the Quaich, a society of whisky experts, told BBC radio. "I don't think the master blenders are going to be quaking in their boots but really quite grateful."

Detecting counterfeit whiskies might be the headline-grabbing application for Clark's device, but it could be used to "taste" almost any liquid. He sees the device also being useful for quality monitoring on industrial production lines—food or beverage manufacturers, for instance, keen on ensuring quality control so that their products have a uniform flavor profile. Clark would also like to see it developed for environmental monitoring of water supplies. This would require different metals and different chemicals, but the basic techniques remain the same. His lab is already starting to test various candidates with that application in mind.

DOI: Nanoscale, 2019. 10.1039/C9NR04583J (About DOIs).