As all good whisky enthusiasts and connoisseurs will tell you, a drop of water in your dram enhances the smell and flavor of the smoky, golden liquid. Turning to the slightly unconventional use of computer simulations, scientists have now been able to explain exactly why a dribble of water helps the tipple.
“The taste of whisky is primarily linked to so-called amphipathic molecules, which are made up of hydrophobic and hydrophilic parts,” explained Björn Karlsson, co-author of the study published in Scientific Reports. This basically means that one side of the ‘taste’ molecules in whisky is attracted to water, while the other is repelled by water. And it turns out that this two-ended structure in one such molecule known as guaiacol has a major bearing on the intoxicant's flavor.
Guaiacol is typically found in smoky and peaty Scottish whiskies, and has previously been identified as the cause of this distinctive flavor so beloved by many a whiskey connoisseur. By using computer simulations of water and ethanol mixtures with guaiacol added, the researchers were able to see how the different concentrations of the two liquids changed the behavior of the flavor molecules in solution.
They found that guaiacol is preferentially associated with ethanol, as in it is more likely to bind to the alcohol molecules. When the alcohol concentration is at or above around 70 percent, as it is when it is first barrelled, these alcohol molecules with the guaiacol in tow tend to hover somewhere around the middle of the liquid, essentially keeping the flavor from floating to the surface.
As more water is added, such as during bottling when the concentration is brought down to roughly 45 percent, the alcohol molecules tend to spread out more, meaning more of the guaiacol floats to the surface.
“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 Freidman, who co-authored the research. But they found that this effect apparently doesn’t stop there. “Interestingly, a continued dilution down to 27 percent resulted in an increase of guaiacol at the liquid-air interface.”
This, in turn, results in a more superior flavor, something that whisky enthusiasts could have told you before. While diluting a good whisky down to 27 percent may seem low to some, whisky tasters are known to take it down even further, sometimes as low as 20 percent.
But rather than simply justifying ordering a whisky and water, the research may have some interesting applications in explaining how certain drugs move through the body too.