Dynamic evolution of ethanol clusters and solubility modulation of flavor esters during the aging of Soy sauce flavor Baijiu.

This study elucidates the microstructural evolution of ethanol clusters and their regulatory role in flavor ester solubility during the aging of Soy sauce flavor Baijiu. Using integrated fluorescence and Raman spectroscopy, we show that Liquid-Liquid Phase Separation (LLPS) transforms ethanol clusters from hydrophilic to hydrophobic microdomains. Methodologically, we innovatively combined alcohol dehydrogenase (ADH) activity assay with Nile Red fluorescence probing to distinguish ethanol molecular states. Mass spectrometry further reveals a Non-Monotonic dissolution pattern for four key long-chain fatty acid ethyl esters: initial solubility increase through hydrophobic microdomains is later reversed by steric hindrance due to excessive cluster densification during extended aging. In samples aged over 30 years, pronounced ethanol cluster aggregation triggers flavor precipitation, evidenced by decreased free ethanol and solid deposit formation. These findings uncover the microstructural mechanism linking phase separation to flavor stability, offering a theoretical basis for improving Baijiu colloidal properties and sensory quality.