Why aging matters: Acetaldehyde-acetal interconversion in Baijiu

This study investigates the interconversion between acetaldehyde and its acetal derivatives during the aging process of Baijiu. Acetaldehyde imparts a pungent aroma, while acetal contributes soft fruity and sweet notes to Baijiu. The dynamic equilibrium between these two compounds, mediated by a reversible reaction, significantly influences the aromatic balance and overall flavor harmony of the liquor. By analyzing aging data from Baijiu samples of different alcohol contents (62°, 52°, and 38° ABV) and aromatic types ( Nong , Jiang , Feng , Jian ), we calculated the apparent equilibrium constant (K) and developed a model predicting the simplified equilibrium constant as a function of alcohol content. Results revealed that reduced alcohol content shifts the equilibrium toward acetaldehyde formation, diminishing acetal-derived aromas. This study pioneers a thermodynamic quantitative model for acetaldehyde-acetal interconversion in Baijiu, elucidates the regulatory role of alcohol content in reaction equilibrium through solvent effects. These findings contribute significantly to the scientific understanding of Baijiu aging and offer practical solutions for flavor optimization in Baijiu production, particularly for low-alcohol Baijiu.