This article originally appeared on popsci.com
Your bartender was right, according to a study released today in the journal Scientific Reports. When it comes to whiskey, a touch of dilution improves the solution. Diluting your whiskey with water makes it more flavorful, especially if it’s Scotch.
The reason is guaiacol, an aromatic oil that gives the liquor its signature smoky flavor. Guaiacol is present in guaiacum, a kind of slow-growing shrub with pretty purple flowers, and, as relates to whiskey, the compound is also present in something called wood creosote.
To make whiskey, distillers create a mash, or fermented alcohol solution from a mixture of grains, yeast and water. If you’ve ever wondered what, besides spelling, separates American whiskey from Irish whiskey and Scottish whisky, the answer is (at least in part) the ingredients. Broadly speaking, American whiskey (also called bourbon) is usually made from corn; Irish whiskey from a blend of malted and regular barley; Scottish whiskey (Scotch) from only malted barley. After the mash is made with its respective grain, whiskey makers pour it in distillers, or special containers that boil off the methanol—alcohol that famously makes humans go blind. That leaves behind ethanol, the alcohol that we think of as, well, alcohol, along with the flavors of the original mash. The remaining liquid is put to age in charred oak barrels, which is where scotch gains it’s guaiacol. Charring wood creates wood creosote, so as the liquid interacts with the barrel’s walls, guaiacol migrates into the liquor.
Scotch tends to have more guaiacol than other whiskies because it’s made from malted barley, or barley that’s been soaked in water to make it germinate and then heated to stop that germination. In the case of whisky from the Scottish island of Isley, the barley is smoked on peat fire. Both steps add a bit more guaiacol to the mix.
