A competing theory suggests that adding water releases molecules that improve the flavor . Water and ethanol don’ t make for a perfectly uniform mixture. Aromatic compounds could become trapped in ethanol clusters and never reach the surface . Our tongues are only capable of identifying the flavors , sweet , salty, sour , bitter , and umami ( savory ) , so aroma is really important for detecting all the other flavors that connoisseurs appreciate in whiskey .
Karlsson and Friedman did calculations and found that fatty acid esters exist in such low concentrations that the first theory is unlikely , so they decided to focus on the second . In reality , “ whiskey is a complicated mixture of hundreds or even thousands of compounds , ” Karlsson said . They focused on just three : water , ethanol , and an aromatic compound called guaiacol.
Guaiacol is what gives whiskey that smoky , spicy , peaty flavor. Chemically , guaiacol is similar to a lot of other whiskey aroma compounds like vanillin ( with the scent of vanilla ) and limonene ( citrus ) . These and other flavor compounds are not attracted to water and are more likely to become trapped in ethanol clusters .
In the researchers ' simulations , they found that the concentration of ethanol had a large effect on guaiacol. At concentrations above 59 percent ethanol ( the alcohol content to which whiskey is distilled ) the guaiacol was mixed throughout . Whiskey is diluted before bottling to about 40 percent ethanol . In the simulation, at 40 percent , ethanol accumulated near the surface , bringing the guaiacol with it . At about 27 percent the ethanol began to aerosolize , presumably freeing the guaiacol even further .
If their state of the art simulations were a SIMS video game , you would play the role of a stressed out bartender and spend hours adjusting the water and alcohol levels back and forth. Not enough water, and the guaiacol won ’ t bubble up into the nostrils of your whiskey - swilling patrons. Too much , and your angry customers spit out the flavorless , watered down spirits .
“ Adding water changes the equilibrium , ” said Daniel Lacks who was not involved with the study , but conducts similar modeling experiments at Case Western University . The new model shows that diluting the whiskey “ causes molecules to rise to the surface . ”
But Paul Hughes , a food scientist and distilling expert at Oregon State , was not convinced that the propensity of ethanol to rise to the surface when whiskey is diluted tells the whole story . In the simulation , only three types of molecules were included, and their activity was modeled in a very tiny volume of spirits . “ My sense is that the box they’ ve used isn ’ t tall enough , ” Hughes said .
The ratio of surface area to volume in the simulation is not at all similar to what you get with a bottle or a glass, he said . He predicts that disruption of the ethanol clusters within the bulk of the whiskey may also be important .
Whether by disrupting ethanol clusters or encouraging the molecules to rise to the surface , it ’ s clear that adding water to whiskey has the molecular potential to release important flavor compounds like guaiacol. So why isn ’ t whiskey simply bottled at lower alcohol concentrations ?
If diluting whiskey really does mean that aromatic molecules evaporate from the surface , “ by bottling at higher concentrations , you get less deterioration of taste , ” Lacks said . Whiskey , by definition , has to be 40 percent alcohol , said Hughes . Diluting it would also increase packaging and distribution costs and take away the choice from the consumer .
At the end of the day , individuals should drink their whisky however they prefer it , said Hughes , but “ if someone says they don ’ t like whiskey , ” he added , “ they just haven ’ t tried the right one yet . ”