Study on the antioxidant activity of black highland barley under different thermal processing methods based on targeted metabolomics

Black barley, a staple cereal uniquely adapted to the Qinghai-Tibet Plateau, is rich in anthocyanins. This study investigated four thermal processing methods: baking, steaming, stir-frying, and boiling. Total anthocyanin content (TAC), DPPH/ABTS radical scavenging capacity, and Fe²⁺ chelation ability were determined. Targeted metabolomics based on LC-MS/MS was also performed. All thermal treatments decreased TAC, with boiling causing the greatest reduction. Under the tested conditions, stir-frying achieved the highest total anthocyanin retention and antioxidant activity retention among the four thermal processing methods. A total of 41 differentially abundant metabolites were putatively identified at MSI Level 2. Acylated anthocyanins, including pelargonidin 3-(6″-acetylglucoside) and cyanidin 3-(6″-acetyl) galactoside, were detected at higher levels in the stir-fried group. These metabolites showed strong positive correlations with antioxidant activity, suggesting that acylated derivatives may contribute to enhanced thermal stability and bioactivity. Under the traditional processing parameters employed in this study, stir-frying is conducive to preserving anthocyanin stability and antioxidant capacity in black barley. These results provide practical insights for the processing and utilization of black barley in functional foods.