Dynamic changes of flavor characterization of lager beer during barrel aging process based on untargeted volatilomics

Oak barrel aging induces complex, time-dependent transformations in beer flavor. This study systematically characterized these changes through a 300-day aging experiment integrating quantitative sensory analysis, physicochemical monitoring, and HS-SPME-GC-MS-based volatile metabolomics. Barrel aging introduced distinct coconut and vanillin notes, with extended aging further intensifying woody, sweet, and caramel characteristics, while wine-like notes remained stable. Volatile profiling identified 162 significantly differential metabolites across 12 chemical classes, including esters, aromatic compounds, ketones, and heterocyclic compounds. Mantel correlation analysis revealed that three wood-derived volatiles-(Z)-oak-lactone, ethyl 2-furoate, and (2,2-diethoxyethyl) benzene-were strongly correlated with aging time (|r| > 0.8) and served as potential biomarkers. Notably, (Z)-oak-lactone was quantitatively linked to both "woody" and "sweet" odor notes (r > 0.89). These findings establish a predictive chemical-sensory framework for understanding flavor development during barrel aging.