Per World Whisky Day, the smoky flavor of peated whisky is derived from the compounds released by burning peat. No, burning peat isn’t placed into whiskey barrels. Instead, peat is burned beneath the kilns in which whisky malts are left to dry and roast. As rich smoke from the peat rises, the malt grains are dried, leaving them with a unique, earthy flavor. The process can take up to 15 hours as the aromas fully infuse the malt grains with smoky notes resulting from ashy-tasting phenols.
According to Drink Hacker, these phenols are a complicated class of aromatic compounds that can include phenol, cresols, xylenol, and guaiacol, with each influencing whiskies’ flavors in unique ways. However, they don’t necessarily correspond to the smokiness of a whisky, according to Distiller, who offers the example of Lagavulin and Caol Ila as comparative examples.
While both labels use the same peated barley to make whisky, the final product varies in levels of smokiness. This is because phenols deviate throughout the whisky production process, specifically when they are in the barrel, where they are able to “fully oxidize, becoming more complex” per Drink Hacker.