The study of fermentation loach promoting the formation of umami-antioxidant peptides in Yu jiaosuan and its underlying mechanisms

Yu jiaosuan (YJS) is a traditional fermented chili–fish paste from Southwest China, known for its distinctive flavor and rich umami characteristics. To address the shortage of raw materials and elucidate the formation mechanisms of umami–antioxidant peptides in YJS, cultured loach was employed as a substitute for Beaufortia kweichowensis . Metabolomics and peptidomics analyses revealed that umami peptides mainly originated from the hydrolysis of loach myosin heavy chain, actin, and tropomyosin. These peptides reached their highest levels on day 12 of fermentation, with six peptides (EGF, FDH, PDM, ADLF, FYDG, WGD) exhibited dual umami and antioxidant activities. FYDG, WGD, and FDH showed low umami thresholds (0.28 mg/mL, equivalent to 0.01–0.02% w/v MSG). This was confirmed by electronic tongue analysis and sensory evaluation. FYDG and WGD displayed strong antioxidant activity, scavenging 46.61% of DPPH and 36.96% of ABTS radicals. Molecular docking indicated stable interactions with T1R1/T1R3 and Keap1 receptors. Moreover, Lactococcus and Leuconostoc were positively correlated with umami peptide accumulation and contributed to maintaining a low-pH (≤3.75) antibacterial environment. These findings elucidate the synergistic formation mechanism of umami–antioxidant peptides in fermented loach-based YJS. Together, they provide a theoretical foundation for developing natural flavor enhancers. Future studies should focus on validating peptide bioactivity in vivo and optimizing microbial regulation during fermentation. • Peptidomics and machine learning were used to identify dual-function peptides. • Six peptides exhibited both umami taste and antioxidant propertides. • FYDG and WGD showed strong umami intensity and radical scavenging activities. • Docking revealed T1R1/T1R3 and Keap1 binding, explaining dual functionalities.