How and why does water enhance the taste of whisky?

It all gets back to the chemistry of the flavour compounds in whisky, Björn Karlsson and Ran Friedman, researchers at Linnaeus University in Sweden, found.

“The taste of whisky is primarily linked to so-called amphipathic molecules, which are made up of hydrophobic and hydrophilic parts. One such molecule is guaiacol, a substance that develops when the grain is dried over peat smoke when making malt whisky, providing the smoky flavour to the whisky,” Karlsson explained.

At ethanol concentrations between 27% and 45%, amphipathic molecules like guaiacol are more likely to be found near the liquid-air interface than in the bulk of the liquid. So when the consumer sniffs or sips their whisky they immediately perceive the flavour. If the alcohol content is above 59% the flavour molecules are more likely to be away from the liquid-air interface and so less likely to be enjoyed as readily by the consumer.

To find out the whole story read the article Dilution of whisky — the molecular perspective, which has been published online by Scientific Reports.