Molecular Characteristics and Thermal Stability of Salty/Saltiness-Enhancing Peptides from Enzymatic Hydrolysates of Agaricus bisporus

Agaricus bisporus peptides with a saltiness-enhancing effect (24%) were obtained through favorable enzymatic hydrolysis conditions. To identify the molecular characteristics of saltiness-enhancing peptides, A. bisporus protein was extracted and hydrolyzed under the selected optimal conditions. The resulting peptides were further separated through ultrafiltration and gel chromatography and characterized by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Molecular docking was then performed with the transmembrane channel-like 4 (TMC4), leading to the identification of four key peptides: WDDVRGW, GRGGYFDEF, ARSIGVS, and WDEVRGE. The synthetic WDDVRGW was proved to be a salty peptide and saltiness-enhancing peptide. The aqueous solution of 0.05% WDDVRGW displayed a saltiness of 3.66 ± 0.13, and 0.005% WDDVRGW with 0.4% NaCl solution presented a saltiness of 4.93 ± 0.05, showing a saltiness enhancement of 11.4%. Both synthetic and enzymatic hydrolyzed peptides exhibited higher saltiness-enhancing effects at lower NaCl concentrations. A. bisporus peptides can maintain a high saltiness-enhancing effect (>15%) after the thermal process at 105–125 °C for 120 min, exhibiting desirable thermal stability. The initial pH of 8.0 in the thermal reaction solution was more beneficial to the formation of saltiness-enhancing peptides.