Have you ever wondered why adding water to your whisky, which lowers its alcohol percentage, opens up different and subtle, new flavors? Or why a glass of wine tastes less fruity than non-alcoholic grape juice? Sit back, pour yourself a glass and take this crash course on taste perception to learn how different aromas are affected by alcohol.
Start with a deep inhale over your glass of wine. Can you describe what you smell? Possibly some nutty, fruity or even rose-like notes? Thanks to our sense of smell, humans can differentiate between up to 10,000 different odors, although we can't pinpoint them all! This is because of their 'detection threshold.' It's the minimum concentration of an aroma that must be present in order for us to perceive it. Odors, known as smells, scents and fragrances, consist of one or more aroma molecules. Aromas are volatile and reach our sense of smell via 'headspace,' which is the air space directly above the surface of liquids.
We perceive aromas through our noses (orthonasal), as well as through the mouth (retronasal). Each time we swallow, aromas travel up through the back of our throats and into the nasal passage. This explains why wine experts employ seemingly odd-sounding techniques to aerate their wine (and the aromas). Doing so allows them to not only avoid swallowing the alcohol, but to detect more of the wine's volatile aromas molecules.
"Many factors influence which odors we can detect in the headspace while drinking. The physical characteristics of different aroma molecules is a key determinant."
Hydrophobic versus Hydrophilic
Every aroma molecule behaves differently in solvents, depending on their physical properties. As the term suggests, hydrophobic aroma molecules are water-adverse. They tend to flee when surrounded by water molecules, exiting into the headspace where they are easier to detect with our sense of smell. Conversely, hydrophilic aroma molecules have an affinity for water molecules and prefer to remain in liquids.
Alcohol (ethanol) has partially hydrophobic properties. This explains why the hydrophobic aroma molecules found in alcoholic beverages still remain in your wine and spirits despite the presence of alcohol.
"The proportion of liquids—water versus alcohol—determines which aromas are easier to detect than others. The more alcohol there is in your drink, the more hydrophilic aromas will escape to the headspace."
On the other hand, the higher the volume of water, the more hydrophobic aromas you'll have escaping from the liquid and moving into the headspace. An aromatic comparison of Gewurzstraminer wine with and without alcohol demonstrates the marked difference in flavor.
As we can see from the chart, non-alcoholic Gewürzstraminer contains more floral aromas than a glass of its alcoholic version. Moreover, the juice's fruitiness is also more pronounced.
"In the absence of alcohol, the Gewürzstraminer's floral molecules escape into the headspace and cause the wine to smell more flowery."
The next time you raise your glass, you can credit your wine tasting experience to this very delicate balance of water versus alcohol. Thanks to the presence of the latter, we get to enjoy the subtle, nuanced flavors of our favorite wines and liqueurs and even pair them with food!