Abstract: In this work, the hydrogen bond interactions between ethanol and water, between ethanol and flavor compounds, between water and flavor compounds, and among ethanol, water and flavor compounds were investigated by quantum chemistry calculation to provide insights into the mechanism of Baijiu aging. The results density functional theory showed that the structural stability of the binary and ternary complexes was in the decreasing order of ethanol/water-acid > ethanol/water-alcohol > ethanol/water-ester, and ethanol-water-acid > ethanol-water-alcohol > ethanol-water-ester, respectively. The carbonyl oxygen atom and hydroxyl hydrogen atom in the organic acids could form hydrogen bonds with the hydrogen atom and oxygen atom in the hydroxyl group of ethanol or water, separately, causing the ethanol/water-acid and ethanol-water-acid complexes to form ring structures and consequently improving the structural stability. This may partially explain why the flavor components of Baijiu showed an increase in acids and a decrease in esters during storage and may also explain why storage could strengthen the hydrogen bond interactions and reduce free molecules in Baijiu.

Key words: Baijiu storage; quantum chemistry; flavor compound; hydrogen bond; interaction