Roles of soy protein isolate in improving gelling properties of fish balls made from silver carp

In this study, the texture, water holding capacity, surface hydrophobic groups and microstructure of the fish balls, made from silver carps, were measured to study the effect of different addition ratios of soy protein isolate (0%, 2%, 4%, 6% or 8%) on the gel strength of fish balls. The results showed that the gel strength, springiness and water holding capacity of fish balls increased steadily with the amount of soy protein isolate added increasing, and the resilience of fish balls was increased to the maximum level (7 492.85 g) by adding 4% soy protein isolate while the rest was lower than the control. Compared with the control, the adhesiveness of fish balls was significantly decreased by incorporating different proportions of soy protein isolate. The incorporation of soy protein isolate also slightly reduced the cohesiveness of fish balls from 0.84 (soy protein isolate-free fish balls) to 0.82 (all fish balls incorporated with soy protein isolate). The protein denaturation temperature of the control was 100.49°C, and that of soy protein isolate-containing fish balls increased with the amount of soy protein isolate increasing, till the maximum value (107.23°C) was reached at 8% soy protein isolate. The results of SEM and FTIR showed that the number of disulfide bonds on the surface of surimi proteins gradually increased with the amount of soy protein isolate increasing, and as a result, the surface microstructure of the fish balls was improved. In conclusion, the optimal proportion of soy protein isolate added into fish balls is 4% (gel strength of 2501 N/cm2, water holding capacity of 96.28% and protein denaturation temperature of 99.59°C). © 2019, Asian Association for Agricultural Engineering. All rights reserved.