A fact everyone knows but no one knows why, the research is out, whisky tastes better with water. Whisky drinkers knew this from ages and they didn’t ask for scientific theory but now that’s available, we will raise a glass for it.
Whisky is distilled to around 70% alcohol by volume (vol-%) then diluted to about 40 vol-%, and often drunk after further slight dilution to enhance its taste. The taste of whisky is primarily associated with amphipathic molecules, such as guaiacol, but why and how dilution enhances the taste is not well understood. Scientist carried out computer simulations of water-ethanol mixtures in the presence of guaiacol, providing atomistic details on the structure of the liquid mixture. Researchers found that guaiacol is preferentially associated with ethanol, and, therefore, primarily found at the liquid-air interface in mixtures that contain up to 45 vol-% of ethanol. At ethanol concentrations of 59 vol-% or higher, guaiacol is increasingly surrounded by ethanol molecules and is driven to the bulk. This indicates that the taste of guaiacol in the whisky would be enhanced upon dilution prior to bottling.
Whisky is a spirit that is produced in an extended process consisting of distillation of fermented grains, ageing and dilution. It is through this process that the distinctive taste of whisky develops. Distilled malt whiskies typically contain around 70% alcohol by volume (vol-%) before it is aged in barrels for at least three years. Some alcohol evaporates during the maturation resulting in an alcohol content of 55–65 vol-% of cask-strength whisky. Before bottling, the whisky is diluted to around 40 vol-% by the addition of water, which changes the taste significantly. Whisky enthusiasts often also add a few drops of water to the spirit before drinking in order to further enhance the taste. Apart from water and alcohols,
Whisky enthusiasts often also add a few drops of water to the spirit before drinking in order to further enhance the taste. Apart from water and alcohols, whiskies contain different organic compounds that contribute to their taste. Many whiskies, especially those that are made on the Scottish island of Isley, have a typical smoky taste that develops when malted barley is smoked on peat fire. Chemically, the smoky flavour is attributed to phenols, and in particular, guaiacol, which is much more common in Scottish whiskies than in American or Irish ones.
Guaiacol is a small and mostly hydrophobic molecule that is able to interact with polar solvents via hydrogen-bonding and polar-aromatic interactions. Higher concentrations of guaiacol have been found in Scottish whiskies than in American and Irish ones. The concentration of guaiacol was found by GC/MS to be 3.7–4.1 mg L−1, or about 3.2·10−5 M in two undisclosed Scottish whiskies. It is likely that the concentration of guaiacol in Isley whiskies is even higher. Yet, how diluting whisky with water affects its taste is not clear.