Carboxymethyl chitosan-assisted formation of stable soy protein isolate emulsions and their impact on the properties of squid (Dosidicus gigas) surimi gel

In this study, emulsions co-stabilized by soy protein isolate (SPI) and carboxymethyl chitosan (CMCS) were prepared and the effects of different SPI/CMCS ratios (1:0, 4:1, 2:1, 1:1, 1:2, 1:4) on the emulsification characteristics, rheological properties, and microstructure of the composite emulsions were investigated. Subsequently, the effect of these emulsions on the gel properties of squid ( Dosidicus gigas) ) surimi was evaluated. The results indicated that the particle size, interfacial tension and creaming index decreased with increasing CMCS ratio, while the percentage of interfacial protein adsorption increased. The particle size and interfacial tension reached a minimum value, and the interfacial protein adsorption peaked at the optimal SPI/CMCS ratio (1:2, w/ w). Additionally, CMCS altered the secondary structure of the protein when complexed with SPI, resulting in a more ordered internal structure. Upon adding an appropriate amount of CMCS-proportioned composite emulsion to the surimi gel, significant improvements were observed in hardness, gel strength, whiteness, immobilized water and decreased drip loss and free water. However, over-addition of CMCS resulted in the quality deterioration of surimi gel. Single SPI emulsions had minimal effects on the surimi gel, indicating the superiority of composite emulsions. In conclusion, the SPI/CMCS composite emulsions enhanced the gel properties of surimi gel, offering new avenues to enhance the quality of emulsified surimi-based products.