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martyb writes:

Researchers at Linnaeus University report Why whisky tastes better when diluted with water:

Whisky is a chemically complicated beverage. After malting, mashing, fermentation, distillation and maturing, for at least three years in oak barrels, the whisky is bottled. However, first it is usually diluted to around 40% of alcohol by volume by the addition of water, which changes the taste significantly. For that same reason, whisky enthusiasts often add a little water in their glasses.

But why and how does water enhance the taste of whisky? Up until recently, no one had been able to answer this question, but now Björn Karlsson and Ran Friedman, researchers in chemistry at Linnaeus University, have 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. 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 explains.

Karlsson and Friedman 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% 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. Interestingly, a continued dilution down to 27% resulted in an increase of guaiacol at the liquid-air interface. An increased percentage, over 59%, 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 continues.

Wikipedia: guaiacol.

The full-length, open-access report: http://nature.com/articles/doi:10.1038/s41598-017-06423-5

Original Submission