Evolution of physicochemical properties, bioactive components, and flavor-related compounds during the fermentation of safflower-oat vinegar

This study elucidated the dynamic changes in physicochemical properties, bioactive components, and flavor compounds during safflower-oat vinegar fermentation using MS-based techniques and multivariate analysis. During fermentation, pH decreased to 3.25, while total acidity increased to 55.65 g/L. Total sugar and reducing sugar declined to 1.64 g/100 mL and 0.95 g/100 mL, respectively, accompanied by a gradual darkening of the vinegar. Total phenolic and flavonoid contents initially decreased and then increased, reaching 26.48 mg/100 mL and 14.02 mg/100 mL, respectively, contributing to strong antioxidant activity (DPPH scavenging rate: 93.84%). Total free amino acids reached 903.48 μg/mL at the endpoint, with sweet amino acids predominant (273.89 μg/mL). The major organic acids were acetic acid (55.69 mg/mL) and lactic acid (2.82 mg/mL). A total of 115 volatile compounds were identified during the safflower-oat vinegar fermentation, with esters (645.65 μg/L), acids (370.20 μg/L), and alcohols (558.60 μg/L) dominating the final profile. In particular, isoamyl acetate, phenylethyl alcohol, phenethyl acetate, and benzaldehyde were enriched during the late fermentation, which impart fruity, floral, and almond-like aromas. These findings address the lack of systematic knowledge on safflower-oat vinegar fermentation, providing a reference for product innovation and quality evaluation in functional vinegar.