On the rocks, neat, with a splash of water. How do you drink your whiskey? Well, turns out if you drink it neat, you’re doing it wrong.
A study published in the journal Scientific Reports last month proved that adding water boosts the concentration of flavor compounds at the surface of the whiskey, improving the aroma and taste.
To investigate why adding water improves flavor, the study’s authors, Björn Karlsson and Ran Friedman, developed a computational model looking at the interactions of water, ethanol and a flavor compound called guaiacol. Guaiacol is responsible for that smoky, peaty flavor and aroma found in whiskey.
The interplay of the various chemicals in whiskey is actually quite complex. One end of the ethanol molecule is attracted to water, while the other end is repelled by it. At low concentrations, the ethanol gathers at the surface, with the water-repelling side facing toward the air. At higher concentrations, the ethanol can’t all fit at the surface, so it sinks into the rest of the liquid in clusters.
The guaiacol is more strongly attracted to the ethanol molecules than the water molecules, and can become trapped in ethanol clusters. When the ethanol concentration is too high, and therefore not at the surface of the drink, the tasty, aroma-filled guaiacol molecules are not at the surface either. This impacts the aroma of the alcohol, and in turn, the taste.
Here’s how it breaks down. In the distillery, whiskey can be more than 60 percent alcohol by volume, but is typically distilled to 40-45 percent. At these concentrations, the ethanol (and guaiacol too) sinks. When the whiskey is distilled to 27 percent, the ethanol spreads more uniformly, and the density of guaiacol at the surface is raised by more than a third.
Put simply: “What came out from our study is that adding water to whiskey should make it taste better,” said Karlsson.
Adding water has the added effect of preventing that overwhelming taste of alcohol sometimes present in whiskeys, allowing some of the more delicate flavors to come forward. “The other factor is . . . reducing the alcohol sensation on the nose and tongue,” said David Williamson of the Scotch Whiskey Association.
So why not just bottle the whiskey at 27 percent?
“By bottling at higher concentrations, you get less deterioration of taste,” explained Daniel Lacks, who conducts similar modeling experiments at Case Western University. Bottling at a higher concentration also prevents flavor compounds from escaping when the bottle is opened.
The big question: did the study change how the authors drink their whiskey? Well, it turns out that neither of them are big whiskey drinkers and haven’t yet put their research to the test. But Karlsson concedes, “after this attention we’ve got, it seems like I’m more or less forced to drink it.”