Optimization of Anchovy–Threadfin Bream Composite Surimi: I-Optimal Mixture Design for Sensory Enhancement and Impact Assessment of Three Exogenous Proteins

) is a highly abundant but underutilized fish resource in China, primarily due to its extreme post-harvest perishability. This study expanded the utilization of anchovy by developing a blended surimi from anchovy and golden threadfin bream, an I-optimal mixing design experiment was performed to optimize the formulation, and the effects of soy protein isolate (SPI), egg white powder (EWP), and yeast protein (YP) on the gel properties were investigated. The results of sensory evaluation and model prediction indicated that SPI had the most pronounced positive effect on the sensory characteristics of the gels, especially improving the elasticity, followed by EWP. Furthermore, the SPI-rich sample exhibited superior gel strength and chewiness, which was attributed to the increased β-sheet structure and the highest content of disulfide bonds in the protein network. And the water hold capacity of SPI-rich sample increased by 6.0%. The YP-rich group showed the strongest hydrophobic interactions and exhibited a significant enhancement in water hold capacity of 7.7%, which also provided a notable improvement in gel strength. The results showed that EWP contributed to the smoothness of the surimi, but it had no significant impact on water distribution, water-holding capacity, or the content of disulfide bonds within the gel network. Moreover, the EWP-rich group exhibited reduced the gel strength, hardness, and chewiness of the gel, resulting in the lowest overall sensory score of the surimi. Therefore, the optimal composite ratio was determined to be SPI:EWP:YP = 5.45%:2.55%:2.00%. These findings provided a precise blending strategy for developing high-quality surimi products from anchovy, offering a viable technical pathway for the value-added utilization of this resource.