Salinity-dependent changes in Retronasal detection and dose-over-threshold of kokumi peptides in fermented soybean...

Kokumi is a taste-enhancing sensation that adds complexity, mouthfulness, and continuity by modulating basic taste perceptions. γ-Glutamyl peptides, abundant in fermented foods, are known kokumi-active compounds. This study examined how salinity influences retronasal detection thresholds and dose-over-threshold (DoT) values of nine γ-glutamyl peptides commonly found in fermented soybean paste (doenjang). Most peptides showed higher best estimate threshold (BET) values as salinity increased, indicating reduced retronasal detectability. However, γ-Glu-Phe (γ-EF) showed decreasing thresholds and consistently maintained a DoT >1 across all salinity levels, suggesting stable, salt-resistant kokumi activity. To explore underlying mechanisms, pKa values of selected peptides were measured under different salinity conditions. No significant or consistent shifts were observed, indicating salinity's effect may not be related to ionization but rather to receptor-level interactions. Overall, γ-EF was identified as a key kokumi-active peptide in doenjang, and findings offer insights for improving kokumi flavor in fermented foods with reduced or varying salt levels.