The Scientific Reason You Should Add a Splash of Water to Your Whiskey

A computer simulation shows that diluting whiskey brings flavor molecules to the surface, improving the aroma and taste of the tipple

Scott Schiller /Flickr CC

True whiskey experts have been telling fellow imbibers for years: add a bit of water to your whiskey. The claim is that by adding a touch of water flavors open, improving the taste. Now as Jenna Gallegos reports for The Washington Post, a new study in the journal Scientific Reports gives a thumbs up to the practice and uses science to show why a bit of H2O is good for the brown stuff.

The idea for the study came to Ran Friedman of the Linnaeus University Center for Biomaterials Chemistry in Sweden when he visited Scotland. Gallegos reports that he noticed local drinkers added water to even the most rarified Scotches. (For those not in the know, Scotch is whiskey made in Scotland, primarily from malted barley. Scotts spell the drink whisky, without the 'e.') 

Like a good scientist, he decided to investigate if this practice really did change the flavors of the local tipple and if so, how.

Friedman and his colleague Bjorn Karlsson turned to computer modeling to answer those questions, writes Merrit Kennedy at NPR, simulating how the molecules in Scotch interact with one another. While whiskey has thousands of compounds that impact taste, the researchers focused on three: water, ethanol and a compound called guaiacol that gives the drink its smoky flavor.

They simulated what happens to the Scotch in a small square glass at various alcohol concentrations. Similar to many flavor compounds, guaiacol tend to get trapped by ethanol molecule clusters, reports Sophia Chen at New Scientist. At alcohol concentrations above 59 percent, those flavor compounds are clustered throughout the whiskey. But if it is diluted to about 25 percent, the ethanol and the guaiacol rise to the surface, to an area the researchers call the top of the liquid. It’s likely other similar flavor compounds in whiskey behave the same way.

The simulation indicates that concentrating the flavor molecules at the surface improves both the aroma and taste. “The first thing that you will experience on the tongue is what’s on the interface [between liquid and air],” Karlsson tells Kennedy.

Paul Hughes, a distilling expert at Oregon State University who was not involved in the study, tells Gallegos that the simulation probably doesn’t tell the whole story. Using only three compounds, it's a pretty simple model. The small cube the researchers used as the modeled vessel may also not accurately represent the surface area of the glasses and bottles that whiskey normally comes in, he notes.

So what is the optimum dilution level? Manufacturers have known there’s an alcohol-content sweet spot for whiskey for generations. While most whiskey is about 65 percent alcohol when first produced, manufacturers usually dilute it to around 40 percent when bottling. Technically, alcohol cannot be sold as whiskey if it drops below that level. But how much the drinker dilutes it after that is a matter of personal preference, Huges tells Chen.

And there’s also the possibility of ruining the whiskey with water. “We have receptors on our tongue, in our nose, that are sensitive and depend upon the concentration of the specific components you want to detect with your nose and tongue,” Karlsson tells Kennedy. “So if it's too diluted there's a risk that you actually don't detect it with your nose or your tongue.”

Which would be a great excuse to order another round and try again.

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