Characterization and functional properties of umami peptides from Douchi: taste mechanism and antioxidant activity

Douchi (DC) is a traditional Chinese condiment renowned for its rich umami flavor. This study aimed to comprehensively investigate the composition, characteristics, potential taste mechanisms, and antioxidant activity of umami peptides in DC. The aqueous extract of DC underwent ultrafiltration and gel column chromatography to isolate its high umami components. Three novel umami peptides (EEQEHT, FED, AEPE) were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with bioinformatics analysis. Electronic tongue studies confirmed the high umami activity of these peptides, with scores ranging from 7.64 to 8.72 at a concentration of 0.2 mg/mL, with FED exhibiting the highest umami intensity, minimal bitterness and pronounced saltiness. Molecular docking studies revealed that all three umami peptides were embedded within the T1R1 subunit, facilitating their binding to the umami receptor via hydrogen bonding. Additionally, these peptides demonstrated significant in vitro antioxidant activities, scavenging 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals. In vivo assessments on zebrafish embryos exposed to oxidative stress showed improved survival rates, normalized heart rates, and dose-dependent reductions in reactive oxygen species (ROS) levels. In conclusion, this study provides valuable insights into the umami peptides present in DC, highlighting their potential applications in the food and health supplement industries.