Effect of Zinc-Chelating Phosphorylated Sea Cucumber Peptides on Gel Properties of Mackerel Surimi

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 (7979.10 N), chewiness (4479.42 mJ), viscosity (8032.10 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.