Construction of squid (Dosidicus gigas) surimi gel based on soy protein isolate/carboxymethyl chitosan O/W emulsion: Insights into protein structural and antioxidant properties

This study investigated the effects of an oil-in-water emulsion composed of soy protein isolate (SPI) and carboxymethyl chitosan (CMCS) on the protein structure, microstructure, and antioxidant properties of squid surimi gel. SPI-to-CMCS ratios were set as 1:0 (S1C0), 4:1 (S4C1), 2:1 (S2C1), 1:1 (S1C1), 1:2 (S1C2), and 1:4 (S1C4). The results indicated that increasing the CMCS content of SPI/CMCS composite solution reduced particle size and enhanced the three-phase contact angle, with the S1C2 group achieving optimal stability (particle size:512.2 nm; three-phase contact angle: 64.08 °C). The complexes formed via an electrostatic complexation improved emulsion stability and antioxidant properties. Incorporating the emulsion with the optimal CMCS ratio (S1C2) into surimi significantly enhanced hydrophobic interactions and disulfide bonds, forming a structurally compact gel network. In conclusion, the SPI/CMCS O/W emulsion not only altered the protein structure but also imparted exceptional antioxidant properties, preserving product quality. These findings provide a theoretical reference for future studies on emulsion-surimi gel interactions. • SPI/CMCS O/W emulsion as active fillers improved the protein structure of surimi gel. • The antioxidant properties of the emulsion and emulsified surimi gel were evaluated. • SPI/CMCS O/W emulsion enhanced the chemical bonds of surimi gel as CMCS increased. • Emulsified surimi gel formed a denser and more uniform network structure.