Identification of novel umami peptides in douchi and mechanisms by sensory analysis and molecular modeling

The study aimed to identify umami peptides in douchi and investigate their mechanism of action in terms of umami. Douchi were isolated and purified using ultrafiltration combined with an ion-exchange resin, and their identity was confirmed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Additionally, umami peptides such as TYDGDTEP, VGSEL, FGDEL, IGISIDDH, and RDLL were identified by predictive modeling of umami activity and molecular docking analyses. Sensory evaluation indicated that the umami thresholds for these five umami peptides ranged from 0.5 to 2.0 mg/mL, with TYDGDTEP exhibiting the most potent synergistic umami effect. The umami threshold for peptide TYDGDTEP is 0.5 mg/mL, with a molecular docking binding energy of −111.58 kcal/mol. The molecular docking and molecular simulation results of the five umami peptides identified above reveal that hydrogen bonds and electrostatic interactions are crucial for the formation of umami flavor. Besides, the residues Glu148, Lys155, Glu217, Asn150, Asp218, and Asp219 were identified as critical for binding the five umami peptides to the Taste Receptor Type 1 Member 1/3（T1R1/T1R3）. This study provides a theoretical basis and reference for the processing and application of douchi umami peptides. • TYDGDTEP, VGSEL, FGDEL, IGISIDDH, and RDLL were isolated and identified from douchi. • Screening of umami peptides by molecular modeling and revealing their umami mechanisms. • Hydrogen bonding and electrostatic interactions are key to umami formation. • The umami thresholds of the five umami peptides ranged from 0.5 to 2.0 mg/mL. • TYDGDTEP has significant umami, saltiness, and flavor enrichment effects.