The Science of Whiskey!

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Drinking alcohol may lower our inhibitions and make us generally feel more sociable, but sometimes ordering alcohol at a bar can be a daunting experience if you’re not sure what you’re doing. Take whiskey, for example — whiskey is an incredibly complex drink with thousands of different brands and flavors, with confusing names and labels like single malt, blended, 20-year, 30-year, blue, red, black, Scotch, bourbon, etc. etc. etc. And to make things even more difficult, there are several different ways to drink it: straight up, on the rocks, with water, or in a cocktail.

I happen to like whiskey but I’m relatively uneducated on the subject. It was only recently I learned that adding water to a whiskey can actually do the opposite of what I thought it would do: it can make its taste stronger.

Generally, you add water to a drink to dilute it, which would make it taste weaker, which is why I’ve always avoided doing it. Adding ice to a whiskey, for example, can dilute it to the point where you can’t really taste it at all, especially when the ice decreases the temperature, which is a good way to make any drink less flavorful because your taste buds aren’t good with extreme temperature changes. (That’s why red wines are served at room temperature — you can actually taste every aspect of the wine much better, compared to white wines that are served chilled.)

But it turns out that if you add just a tiny bit of water — a few drops at most — to a glass of very “smoky” whiskey (like many Scotch whiskeys), you can really amp up that smoky taste. The particulars of why this happens aren’t incredibly well-understood, but some intrepid researchers are working on the science behind it.

A new paper has just been published in Scientific Reports that looks closely at the chemical reaction that occurs when water hits your whiskey glass. The primary culprit is guaiacol (pronounced “gwy-eh-call”), a molecule that gives off the peaty, smoky taste in some whiskeys. Guaiacol is amphipathic, meaning that it’s a mixture of hydrophobic and hydrophilic. That means that there’s a part of it that is repelled from water and a part that is attracted to water, which means that guaiacol behaves differently depending on how much water and how much ethanol there is for it to interact with in your glass.

Before whiskey leaves the distillery, it’s usually diluted down to about 40% alcohol by volume. The research shows that this first step is important to making the guaiacol taste more prominent. But when it’s in your glass, that guaiacol is still pretty mixed up in the whiskey. Adding a few more drops of water is enough to push a bunch of guaiacol to the surface of your glass, where you can more easily smell and taste it.

The researchers found that this works best in whiskey up to 45% abv. With higher abv whiskeys, like “cask-strength” of around 59% strength, the guaiacol interacts more strongly with the ethanol, causing it to be pushed down into the mixture and away from the surface (and therefore your nose).

So did science show exactly how much water to add to your whiskey? Nope, because taste remains completely subjective. But it does show us why if you love a peaty whiskey, adding a drop of water to your glass will make it even peatier. You can even try this using just your saliva — take a sip of a peaty whiskey and let it sit in your mouth long enough to generate some saliva. After 15 seconds or so you should be left with an oilier liquid that is super smoky.

It’s pretty cool to learn something about chemistry (traditionally my own personal worst subject) in a way that you can directly try (and taste) for yourself…if you’re over 21 of course. Or over, like, 14 or whatever in Scotland.*

*18. The legal whiskey drinking age in Scotland 18. Drink responsibly, kids, your brains are still developing.

Rebecca Watson

Rebecca is a writer, speaker, YouTube personality, and unrepentant science nerd. In addition to founding and continuing to run Skepchick, she hosts Quiz-o-Tron, a monthly science-themed quiz show and podcast that pits comedians against nerds. There is an asteroid named in her honor. Twitter @rebeccawatson Mastodon Instagram @actuallyrebeccawatson TikTok @actuallyrebeccawatson YouTube @rebeccawatson BlueSky

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