Enhancement of gel properties of low‐salt Scomberomorus niphonius surimi by egg white protein: Structural refinement and intermolecular interaction analysis

BACKGROUND: High-quality gelation of Scomberomorus niphonius (SN) surimi under low-salt conditions remains challenging for the seafood industry. This study evaluated egg white protein (EWP) substitution (1-9%) to enhance the gel properties and water retention of low-salt (1% sodium chloride) SN surimi under reduced ionic strength. RESULTS: The results demonstrated that the optimal performance was achieved at 5% EWP substitution, where the breaking force significantly increased by 58.9% compared to the low-salt control (LC) group, and the water-holding capacity (WHC) concurrently improved to 73.03%. Quantitative cryo-scanning electron microscopy (cryo-SEM) analysis revealed substantial network densification, characterized by a decrease in porosity from 55.67% (LC group) to 34.85% and a minimum mean pore size of 0.25 ± 0.16 μm. Pearson correlation and heat map visualization confirmed that this microstructural refinement (r = -0.921 with WHC) and the enhanced formation of disulfide bonds (r = 0.993 with breaking force) were the primary drivers for the improved water retention and gel strength, respectively. Mechanistically, at moderate substitution levels (≤ 5%), EWP was partially compatible with SN myofibrillar proteins, functioning as a co-gellant and crosslinker via disulfide-related interactions that transformed the loose, porous matrix into a compact honeycomb structure; however, excessive substitution (> 5%) promoted preferential EWP self-aggregation and microphase separation, thereby undermining network continuity and integrity. CONCLUSION: Optimal EWP substitution (5%) effectively overcomes the gelation defects of low-salt SN surimi by forming a co-gel network driven by disulfide crosslinking and structural densification. These findings elucidate the quantitative structure-function relationship of EWP in low-ionic-strength systems, providing a solid theoretical foundation for the development of healthy, salt-reduced surimi products.