Insight into the effects of chitosan on the gelling properties of tilapia surimi gel under microwave heating treatment

This study aimed to assess the effects of chitosan on the gelling properties of tilapia surimi gels during microwave (MW) heating treatment from composite gel layer to myofibrillar proteins (MPs) layer. For composite surimi gel, the hardness, elasticity, and water holding capacity of surimi gel with 0.004 % chitosan (CS) initially increased and then reduced with the increasing MW power (0-9 W/g). Rheometer measurements demonstrated that the samples displayed high elasticity across the entire frequency range (0.1-100 Hz) and exhibited gel-like characteristics. The best apparent morphology of surimi gel was observed at MW power of 3 W/g. To further explain the interaction, MPs solutions with different CS volume ratio (0-10 %) showed significant aggregation and more formation of disulfide bonds. Moreover, ultraviolet and intrinsic fluorescence spectra showed that the surimi samples had protein structural characteristics. Furthermore, molecular dynamics (MD) simulations were used to initially investigate and explain the interactions between MPs and CS under the MW treatment, indicating that MPs/CS complex exhibited higher flexibility and a greater tendency to react and transition into a more compact three-dimensional (3D) network structure during the MW treatment. Therefore, this study provides a deeper understanding of the mechanism involved in microwave-assisted tilapia surimi gel formation, thereby expanding industrial applications of surimi products.