Abstract: This study aimed to explore the effect of phosphorylation on the zinc-chelating capacity of sea cucumber peptides and the gel properties of mackerel surimi. Zinc-chelating peptides were prepared by incubating 50 mg/mL phosphorylated sea cucumber peptides with different concentrations of 5 mmol/L zinc sulfate and characterized for molecular mass distribution, amino acid composition, Fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-Vis) spectra, fluorescence spectra, zinc-chelating capacity, molecular particle size, secondary structure, and surface hydrophobicity. Meanwhile, NaCl, ZnSO4, the phosphorylated peptides, and their zinc chelates were added separately to mackerel surimi to study the effects of zinc-phosphopeptide chelates on the texture properties, microstructure, and flavor of mackerel surimi. The results showed that chelation with zinc sulfate at a mass ratio of 1:1 resulted in significant structural changes in the phosphopeptides, and the zinc-chelating capacity was significantly enhanced. Addition of the resulting product to mackerel surimi resulted in the maximum elasticity (0.98), hardness (7 979.10 N), chewiness (4 479.42 mJ), viscosity (8 032.10 N·s/m2), and cohesiveness (0.92), as well as in the highest umami intensity. Under the action of zinc ions, myosin heavy chains formed large aggregates through cross-linking, resulting a uniform and dense gel microstructure. Therefore, the addition of zinc-chelating phosphorylated sea cucumber peptides mackerel surimi could significantly improve its gel properties.

Key words: zinc ion; phosphorylated sea cucumber peptides; mackerel surimi; microstructure; gel properties