Cold beer has a stronger alcohol flavor than room temperature beer. Temperature affects the way water and ethanol molecules within alcoholic beverages are organized, thereby altering their taste. The same goes for alcohol content, as the chemistry of the mixture changes as the alcohol concentration increases. By combining these variables, the taste of the drink can be optimized.
This finding at the chemical level, which was presented Wednesday in the journal Matter, explains the science behind a knowledge that humans have accumulated based on hundreds of years of evidence. Neither the alcohol content nor the temperature at which different alcoholic beverages are served is random; instead, the goal in each case is to achieve the best flavor for each one. And yet, 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 blends can be optimized to obtain specific flavors,” explains Lei Jiang, a researcher at the Chinese Academy of Sciences and one of the authors of the study to La Vanguardia. Additionally, it provides information on “the ideal temperature at which different alcoholic beverages should be served to enhance the overall sensory experience.”
Jiang and the other authors have seen that, in the end, everything is a matter of order. The water and alcohol molecules that make up beverages do not distribute randomly, but organize into small groups. When the amount of alcohol in the drink is small, water molecules surround the ethanol molecules and form a sort of pyramid that traps them; as the alcohol concentration increases, the structure becomes more “democratic,” and the components organize into chains of alternate molecules. The temperature of the drink also influences this organization.
The quantity of each type of structure determines the flavor of the drink. As chain-shaped structures increase in number, the taste becomes more alcoholic. This is what happens, for example, when the temperature of the mixture is lowered, and it explains why beer or white wine is usually served chilled: they have a stronger alcohol taste.
Something similar happens with high temperatures. When heating the mixtures to 40°C, scientists observed that the proportion of chain-shaped structures increases and, once again, the alcohol flavor is enhanced. Hence, some drinks, such as Japanese sake or Chinese baijiu, 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 completed his doctoral studies. In the midst of their celebration, they wondered why alcoholic beverages always have a specific range of alcohol content: beer typically hovers around 4%, wine falls between 11 and 16%, and whiskey, brandy, and vodka range between 40 and 43%.
In the laboratory, they performed perhaps the simplest test of all: they mixed water and ethanol in different concentrations, ranging from 1 to 99%, and observed what happened when a drop of each was placed on a graphite sheet. Pure water tends to stay in a droplet shape on the surface, while alcohol spreads out completely. This is because water has a higher surface tension than alcohol, meaning it better withstands the force of gravity.
Scientists thought that as the alcohol concentration of the mixture increased, the surface tension would decrease, and the droplet on the surface would become flatter. However, the experiment revealed that the properties do not change progressively, but in jumps.
For example, a mixture containing 42% alcohol behaves almost the same as one with 50%. However, when the ethanol concentration increases from 50 to 52%, the surface tension drops sharply, and the droplet suddenly flattens. Then, it maintains its shape—and surface tension—constant until reaching a concentration of 68%.
This is important because the surface tension of the mixture depends on how its molecules interact. When the shape of the droplet is similar, the proportion of pyramidal and chain structures is also similar, resulting in the same flavor. Ultimately, the flavor of a drink hardly changes regardless of whether the alcohol content is 42% or 50%. However, the difference is significant if it jumps to 52%.
“Our findings will help develop new beverages with the desired flavor profiles at lower ethanol concentrations,” Jiang points out, “something that can contribute to responsible alcohol consumption.”
