Chinese researchers have discovered a connection between alcohol content and temperature that could impact the way companies produce and market beverages.
In a paper published in Matter journal on 1 May, researchers reported that the reason people enjoy cold beer cold and warm baijiu (Chinese whisky) has to do with the way water and ethanol form either chain-like or tetrahedral (pyramid-shaped) clusters at the molecular level.
Chinese Academy of Sciences materials scientist and lead author of the paper, Lei Jiang, said that he was drinking beer with first author Xiaotao Yang when they decided to investigate the matter.
“At the time, I was a scientific committee member of one of the biggest Chinese alcoholic beverage companies, and I had the idea to ask the question ‘why does Chinese baijiu have a very particular concentration of alcohol, either 38-42%, 52-53%, or 68-75%?’”
“Then we decided, let’s try something, so I put a drop of beer on my hand to see the contact angle,” said Jiang.
Contact angle is a measurement used to determine the surface tension of a liquid, acting as an indication of how the molecules are interacting with each other and the surface.
For instance, water has a low contact angle on a glass surface, and so a drop of it will appear “bead-like”, whereas a drop of high alcohol concentration spirits would have a higher contact angle and would spread out.
Jiang, Yang, and a team of researchers decided to measure the contact angle of a series of solutions with increasing concentrations of alcohol in water to see how it responded.
It was discovered that the contact angle did not increase linearly with increasing alcohol concentration, but instead showed an irregular series of plateaus as it increased, due to the formation of different clusters of ethanol and water in solution.
At low ethanol concentrations, the ethanol forms more tetrahedral structures around water molecules; however, when the concentration of ethanol is increased, the ethanol begins to arrange end to end in a chain-like structure.
They also found that the plateaus that they observed disappeared or appeared when the solutions were cooled or heated, and that some of these trends could explain differences in how alcohol taste is perceived.
For example, 38-42% and 52-53% ethanol solutions – like the ethanol concentrations in baijiu – have distinct cluster structures at around room temperature, but this difference disappears at higher temperatures, which was tested at 40°C.
This helps to explain why both professional and amateur tasters can distinguish the concentrations of baijiu at room temperature but not at high temperature. At higher temperatures, both concentrations have more chain-like structures and therefore a more “ethanol-like” taste.
“Although there is only 1% difference, the taste of baijiu at 51% and 52% is noticeably different; the taste of baijiu at 51% is similar to that of lower alcohol content, such as 38%-42%. So, in order to achieve the same taste at a lower alcohol content, the distribution of baijiu products ranges most within the 38%-42% and 52%-53% categories,” said Jiang.
The results of these experiments also showed a distinct enhancement in the chain-like structures at 5°C in 5% and 11% ethanol solutions. This explained why professional testers observed a stronger taste in beer after it had been chilled.
The discovery has the potential for use in the alcoholic beverage industry, to achieve the same tastes for beverages at the lowest ethanol concentration possible.
