Valorization of bigeye tuna (Thunnus obesus) bone by-products via steam explosion: Novel umami peptides with synergistic taste enhancement and sodium reduction potential.

This study developed an integrated approach combining steam explosion pretreatment with enzymatic hydrolysis to isolate umami peptides from tuna (Thunnus obesus) bone by-products. Steam explosion enhanced the hydrolysis efficiency and increased the degree of hydrolysis from 9% to 18%. The ultrafiltration fraction below 3 kDa exhibited pronounced umami and saltiness-enhancing properties. Peptidomics and virtual screening identified three collagen-derived peptides (GPRGAPGPA, GPAGRPGPQ, GAQGPVGAPGPK) with umami detection thresholds between 0.15 and 0.45 mM. Molecular docking and dynamics simulations suggested stable binding to the T1R1/T1R3 receptor (binding energies from -8.1 to -9.0 kcal·mol-1), mediated mainly by hydrogen bonds and hydrophobic interactions. An equimolar mixture of GAQGPVGAPGPK and GPAGRPGPQ showed synergistic enhancement, lowering the umami threshold to 0.08 mM and intensifying saltiness perception. This work offers a sustainable strategy for tuna bone valorization and provides molecular insights for developing natural flavor enhancers and sodium-reducing ingredients.