Cold beer has more alcohol flavor than room temperature beer. Temperature changes the way the water and ethanol molecules inside alcoholic beverages are organized and this, in turn, alters their flavor. Something similar happens with graduation, since the chemistry of the mixture changes as the alcohol concentration increases. By combining both variables, the flavor of the drink can be optimized.
This discovery at a chemical level, which is presented this Wednesday in Matter magazine, explains the science behind the knowledge that humans have accumulated based on hundreds of years of tests. Neither the graduation nor the temperature at which the different alcoholic beverages are served is coincidental, but rather in each case the best flavor is sought for each one. And despite this, the accumulated knowledge still lacks a clear scientific basis.
“Our research provides a new perspective on how the composition of alcohol and water mixtures can be optimized to obtain specific flavors,” explains Lei Jiang, researcher at the Chinese Academy of Sciences and one of the authors of the work, to La Vanguardia. Additionally, he provides information on “the ideal temperature at which different alcoholic beverages should be served to enhance the overall sensory experience.”
Jiang and the rest of the authors have seen that, in the end, everything is a matter of order. The water and alcohol molecules that make up drinks are not distributed randomly, but are organized in small groups. When the amount of alcohol in the drink is small, the water molecules surround the ethanol molecules and form a kind of pyramid that imprisons them; As the alcohol concentration increases, the structure is “democratized,” and the components are organized into chains of alternating molecules. The temperature of the drink also influences this organization.
The amount of each type of structure determines the flavor of the drink. As the chain-shaped ones grow in number, the flavor becomes more alcoholic. This is what happens, for example, when the temperature of the mixture is lowered, and what explains why beer or white wine are usually served cold: they have a more powerful alcohol flavor.
Something similar happens with high temperatures. By heating the mixtures to 40ºC, the scientists observed that the proportion of chain-like structures increases and, again, the alcohol flavor is enhanced. Hence some concoctions, such as Japanese sake or baijiu, a Chinese whiskey, tend to be served hot.
The study began to take shape one afternoon when Jiang was having a beer with his colleague Xiaotao Yang, who had just finished his doctorate. In the midst of the celebration, they asked themselves why alcoholic beverages always have a certain alcohol content range: beer usually ranges around 4%, wine is between 11 and 16%, and whiskey, brandy and vodka range between 40 and 43%.
Already in the laboratory they did perhaps the simplest test of all: they mixed water and ethanol in different concentrations, between 1 and 99%, and checked what happened if they dropped a drop of each on a sheet of graphite. Pure water usually remains as a drop on the surface, while alcohol spreads completely. This occurs because water has a greater surface tension than alcohol, that is, it withstands the force of gravity better.
The scientists thought that as the alcohol concentration of the mixture increased, the surface tension would decrease, and the drop on the surface would become increasingly flatter. However, the experiment revealed that the properties do not change progressively, but rather in jumps.
For example, the mixture containing 42% alcohol behaves practically the same as the one containing 50%. However, when the ethyl concentration goes from 50 to 52%, the surface tension drops sharply, and the drop suddenly flattens. Then, it keeps the shape—and surface tension—constant up to the 68% concentration.
This is important, because the surface tension of the mixture depends on how its molecules interact. When the shape of the drop is similar, the proportion of pyramidal and chain structures is also similar, so the taste is the same. In short, the flavor of a drink practically does not change whether the alcohol content is 42 or 50%. On the other hand, the difference is notable if it jumps to 52%.
“Our findings will help develop new beverages that have the desired flavor profiles at lower ethanol concentrations,” says Jiang, “something that may contribute to responsible alcohol consumption.”
