Whisky connoisseurs have long thought that mixing a few drops of water could enhance the taste of the drink, and now a study has revealed a scientific explanation for why that may be true.
Researchers at Linnaeus University in Sweden have found that adding water to whisky alters the drink's molecules to make it taste better.
Whisky is a chemically complicated beverage. After malting, mashing, fermentation, distillation and maturing, for at least three years in oak barrels, it is bottled. However, first whisky is usually diluted to around 40 per cent of alcohol by volume by the addition of water, which changes the taste significantly.
Researchers solved a piece of the puzzle that will help us better understand the chemical qualities of whisky.
"The taste of whisky is primarily linked to so-called amphipathic molecules, which are made up of hydrophobic and hydrophilic parts," said Bjorn Karlsson, chemistry researcher at Linnaeus University. "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 said.
Researchers carried out computer simulations of water/ethanol mixtures in the presence of guaiacol to study its interactions. They found that guaiacol was preferentially associated with ethanol molecules and that in mixtures with concentrations of ethanol up to 45 per cent guaiacol was more likely to be present at the liquid-air interface than in the bulk of the liquid.
"This suggests that, in a glass of whisky, guaiacol will therefore be found near the surface of the liquid, where it contributes to both the smell and taste of the spirit," said Ran Friedman, researcher in chemistry at Linnaeus University.
"Interestingly, a continued dilution down to 27 per cent resulted in an increase of guaiacol at the liquid-air interface. An increased percentage, over 59 per cent, had the opposite effect, that is to say, the ethanol interacted more strongly with the guaiacol, driving the molecule into the solution away from the surface," Friedman said.
These findings suggest that the taste and aroma of guaiacol, and similar compounds in whisky, are enhanced when the spirit is diluted prior to bottling and this taste may be more pronounced on further dilution in the glass.
"How we experience taste and aroma is highly individual. Some people choose to add ice cubes to their whisky, to cool it down and give it a milder taste. Thus, there is no general answer to how much water you should add to your whisky to get the best taste experience," Karlsson added. The research was published in the journal Scientific Reports.