Whiskey and scotch drinkers have probably been told at least once to put a few drops of water into their glass, rather than drinking the booze neat. But those who say that the flavors "open up" with that bit of water most likely can't say why.
Well, scientists have confirmed that those folks are right -- in some cases, anyway -- and it all has to do with this thing called guaiacol, a molecule found in whiskey.
It also helps to explain why it tastes best when distillers use water to dilute the caramel-colored booze down to around 40 percent alcohol by volume, even though it typically comes out of the distilling process at around 70 percent ABV.
In an article published in the journal Scientific Reports, authors Bjorn C. G. Karlsson and Ran Friedman documented how they used a computer to measure interactions between water and guaiacol. They found that in whiskey with an ABV of 45 percent and lower, the guaiacol rises to the top of the glass, improving the smell and taste.
"This indicates that the taste of guaiacol in the whisky would be enhanced upon dilution prior to bottling," the authors wrote in the journal. "Our findings may apply to other flavor-giving amphipathic molecules and could contribute to optimizing the production of spirits for desired tastes."
But at a higher ABV such as 59 percent, the guaiacol doesn't stay at the surface. Instead, it tends to sink, getting distributed evenly throughout the glass, which means that the aroma isn't as strong or close to your nose. So if you're drinking whiskey, add a couple of drops of water if the ABV is above 45 percent.
If the ABV is much lower than that, you might want to stick to drinking your whiskey neat -- and make sure you don't overdo it.
"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 said, according to NPR. "So if it's too diluted there's a risk that you actually don't detect it with your nose or your tongue."