Structural Feature of Salty/Saltiness-Enhancing Peptides Derived from Coprinus comatus and Their Stability during Subsequent Thermal Treatment and Maillard Reaction

Abstract

Through a quantitative analysis of saltiness perception, favorable enzymatic hydrolysis parameters were confirmed for the preparation of saltiness-enhancing peptide mixtures from Coprinus comatus. The enzymatic hydrolysate was fractionated into four fractions (F1–F4) by gel chromatography, with F3 exhibiting the strongest saltiness-enhancing effect (22% increase). LC-MS/MS analysis of F3 identified 36 peptides, and their secondary structures and interactions with the TMC4 receptor were examined through circular dichroism spectroscopy and molecular docking. Molecular docking analysis revealed Asn588, Ser165, Asp5, and Arg168 as key amino acid residues, with the peptide GDNVGF showing the lowest binding energy. Synthetic GDNVGF (0.01%) in 70 mmol/L NaCl enhanced saltiness by 17%. When 0.7% GDNVGF was added to the aqueous solution, its saltiness was equivalent to that of 36.89 mmol/L NaCl, which suggested that GDNVGF functions both as a saltiness-enhancing peptide and a salty peptide. The taste changes of peptides during thermal reactions were further investigated. The thermal stability of Coprinus comatus peptides was good, but their saltiness-enhancing effect slightly reduced due to thermal degradation. The Maillard reaction further diminished this effect, though the umami level remained satisfactory, offering new insights into using Coprinus comatus peptides as low-sodium salt substitutes.