Specific Flavor Substances of Liqueur Koji Fermented Foxtail Millet Beverage: As Indicators of Flavor Characteristics and Antioxidant Capacity

Liqueur koji-fermented foxtail millet beverages offer distinctive flavors and health benefits, but the interrelationships among flavor compounds, sensory properties, and antioxidant activity remain unelucidated. This study systematically mapped dynamic changes across a standardized 72 h fermentation using chromatographic, electronic sensory approaches, and antioxidant assays. Key results revealed glucose, lactic acid, and succinic acid as primary taste-active indicators through HPLC. Early-stage fermentation (0-48 h) accumulated sweet amino acids, while extended fermentation (60-72 h) significantly elevated bitter amino acids, enhancing flavor complexity. GC-MS coupled with OPLS-DA identified 14 signature aroma markers (rOAV>1 and VIP>1), including isoamyl acetate, decanal, and phenylacetaldehyde, predominantly accumulating in later stages to impart floral, fruity, and fatty notes. Radical scavenging assays demonstrated progressively enhanced antioxidant activity, with correlation analyses confirming dual functionality of taste compounds. Specifically, lactic acid, succinic acid, and glucose strongly correlated with sourness, richness, and sweetness, while phenolic compounds, organic acids (lactic, succinic, and malic acids), trehalose, and amino acids (e.g., Cys, Phe, and Val) served as indicators of antioxidant capacity. These bioactive markers provide practical metrics for flavor and bioactivity assessment, advancing quality optimization in functional millet beverages.