Heat-induced blackening enhances antioxidants and reduces pungency in Allium chinense: Metabolomics insights

Blackening of Allium chinense at 70–80 °C enhanced total acidity and reducing sugars, producing a pleasant sweet-sour flavor. Total phenolic content increased from 10.20 to 94.54 mg GAE/g at 75 °C, with enhanced antioxidant capacity (DPPH 66.73%, ABTS 90.59%, FRAP 113.40 μg AAE/g). Non-targeted metabolomics revealed marked reduction of γ-glutamyl-S-allyl-L-cysteine (GSAC) and related γ-glutamyl dipeptides, responsible for the characteristic pungency of fresh A. chinense , alongside upregulation of terpenoids, alkaloids, and flavonoids (2- to 5-fold). Blackening at 75 °C yielded optimal flavor, color, texture, and bioactivity, with 5-HMF accumulation (166 μg/g) within safe limits. This study provides insights into physicochemical and metabolic changes during blackening, offering a foundation for optimizing functional blackened A. chinense production.