Ethanol-water clusters determine the critical concentration of alcoholic beverages

• Published in: Matter Vol. 7; no. 5; pp. 1724 - 1735
• Main Authors: Yang, Xiaotao, Zheng, Jia, Luo, Xianfeng, Xiao, Hongyan, Li, Peijia, Luo, Xiaodong, Tian, Ye, Jiang, Lei, Zhao, Dong
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.05.2024
• Subjects: MAP 3: Understanding
• ISSN: 2590-2385; 2590-2385
• DOI: 10.1016/j.matt.2024.03.017

Alcoholic beverages are conventionally classified by alcohol by volume (ABV) based on ethanol-water mixture (EWM) concentrations, which is regarded as empirical with little scientific explanation. Here, we find that contact angles of EWMs with different ethanol fractions on highly oriented pyrolytic graphite are non-linear but steplike, while the critical points at step edges surprisingly fit the distributions of ABV. High-frequency proton nuclear magnetic resonance and molecular dynamics confirm different ethanol-water clusters in EWMs, whose structures undergo transitions at the critical points and keep stable in step ranges. Detailed cluster structures contain symmetric tetrahedral and chain-like clusters, and the ratio of the latter increases with higher ethanol fraction, further characterized by attenuated total reflectance infrared spectroscopy. Influence of temperature on clusters probably accounts for preferable changes of “ethanol-like tastes” of low-ABV beers or white wine after cooling and high-ABV shochu or Chinese baijiu after heating. [Display omitted] •Unique wettability of ethanol-water mixtures on the hydrophobic surface•Ethanol-water molecular clusters determine surface tension•Temperature influences ethanol-water cluster structures We discover the unique wettability property of ethanol-water mixtures on the hydrophobic surface. The contact angle of alcohol-water mixtures shows a discontinuous stepwise trend and is not affected by the presence of aromatic compounds or tannin from alcoholic beverages. High-resolution NMR and IR experiments as well as MD simulations confirm that different ethanol-water molecule cluster types are present in alcohol-water mixtures of different concentrations. These cluster structures are influenced by cooling and heating, showing changes in contact angle values and partially explaining the drinking habits for different alcoholic beverages. Our findings have important implications for the development of alcohol production and the setting of scientific standards, and the molecular structure of alcohol-water mixtures will contribute to the interpretation of mechanisms involving alcohol-water solvents in synthesis. Our work proves that the alcohol content distribution and proper drinking temperature for different alcoholic beverages are not based on experience but on scientific explanations of molecular ethanol-water clusters in solutions. For the alcohol industry, this work might partly provide a possible way to determine the concentration and further provide a scientific basis for standardization of alcoholic beverages.