Chemists confirm whiskey actually tastes better when drunk with a little water

A study published in the journal Scientific Reports confirms the bartender’s experience was right. When it comes to whiskey, diluting it with water will make it taste better, especially if it’s Scotch.

The reason is guaiacol , an aromatic oil that gives the wine its characteristic “smoky” flavor. Guaiacol is found in guaiacum, a slow-growing shrub with pretty purple flowers, and related to whiskey, the compound is also present in something called wood creosote.

Chemists confirm whiskey actually tastes better when drunk with a little water
Diluting whiskey with water will make it taste better.

To make whiskey, distillers make a mash or fermented alcohol solution from a mixture of grain, yeast, and water. If you’ve ever wondered what, other than spelling, distinguishes American whiskey from Irish whiskey and Scottish whiskey, the answer is (at least in part) the alcohol’s ingredients. More specifically, American whiskey (also called bourbon) is usually made from corn; Irish whiskey from a blend of common malt and barley; Scotch whiskey from only malted barley. After the mash is made with the respective grain, whiskey makers pour it into distillers or special containers to boil methanol – the alcohol known to make people sober, dazed or even blind. As a result we get ethanol, the alcohol we think of as alcohol, along with the flavor of the original mixture. The rest of the liquid is aged in charred oak barrels, which is where the scotch gets its guaiacol. The process of burning wood to charcoal produces wood creosote, so the liquid interacts with the barrel walls, the guaiacol will migrate into the wine.

Scotch tends to have more guaiacol than other whiskeys because it is made from malted barley or barley that is soaked in water to germinate and then heated to prevent that sprouting. In the case of whiskey from the Scottish island of Isley, the barley is smoked over a peat fire. Both steps add a bit of guaiacol to the mix.

Chemists confirm whiskey actually tastes better when drunk with a little water
Dilution of strong whiskey (69% ethanol) pushes flavor-contributing compounds such as guaiacol to the surface of the liquid, thereby improving perception of guaiacol.

What does this have to do with adding water to your drink?

Unless you’re drinking whiskey through a bent straw, you’re sipping what’s known as the liquid-air interface—top. But because whiskey is more than 50% alcohol, as is the case with some of the finer varieties, guaiacol tends to sink deep in the glass. Adding a little water will move the guaiacol closer to the surface, so you can smell and taste it better, creating a more satisfying flavor.

It would be great if researchers from Linnæus University in Sweden reached this conclusion by simply drinking a lot of whiskey, but instead run computational models to study the distribution of guaiacol in a mixture of alcohol and water with different concentrations. They found that alcohol doesn’t really like to mix with water. At lower alcohol concentrations, it moves up near the rim of the glass. But as the alcohol concentration increases, the alcohol molecules clump together to form larger, denser clusters. Those clusters tend to move to the bottom of the drink, away from your taste buds. Since it’s alcohol that contains guaiacol , this migration takes its flavor with it. Of course, some may argue that the test is in the tasting stage.

Most winemakers will say no, you don’t need water; but in fact the drinker did not give water but dropped a few ice cubes in it. When the ice melts, the wine will take on a number of different flavors that even the drinker may not immediately recognize.

There is one exception, however, and that is to drink the whiskey as it flows out of the barrel: no ice, no water. At that time, the wine has a more natural flavor. But most of us don’t have that opportunity.