Unraveling umami complexity: From exploring umami peptides in fermented soybean curd to molecular elucidation of taste mechanisms

Sufu is a traditional umami fermented soybean curd (FSC). We isolated and identified 25 potential umami peptides using ethanol precipitation, dialysis desalination, resin adsorption recovery, nano-HPLC-MS/MS and virtual docking prediction. The results of sensory experiments showed that 23 of the synthetic peptides presented a lower umami threshold than that of MSG (0.50 mg/mL), and 10 peptides had obvious effects of increasing umami and saltiness. Seven peptides were quantified in FSC by UPLC-QQQ-MS, and the content of one novel umami tripeptide ADL (0.51 +/- 0.03 mg/mL) was four times its umami threshold (0.125 mg/mL). Taste reconstitution experiments revealed that the umami peptides enhanced the umami and saltiness of the simulated system by 24.53% and 24.00%, respectively. Molecular dynamics proved that hydrogen bonding is the main interaction between peptide and receptors. This study is important for understanding and improving the taste quality of FSC.