Study on the mechanism of gel properties enhancement of Tenebrio molitor protein/chitosan composite gels induced by transglutaminase

Tenebrio molitor larva protein (TMP) is a highly promising new sustainable insect protein source. However, the single-phase gel has the defects of poor elasticity and loose structure, which significantly limits its application. This study systematically investigated the regulation mechanism of structure, rheological properties and physicochemical properties of TMP gel of different concentrations of transglutaminase (TGase) and chitosan (CS). The results showed that the addition of TGase at 1.5% CS could effectively improve the microstructure and macroscopic properties of the composite gels, and all gels exhibited typical elastic solid behavior. When the concentration of TGase was 80 U/g, the composite gel exhibited the best gel strength and anti-deformation ability. Its gel hardness (197.89 g), creep recovery rate (80.83%) and water retention capacity (40.22%) all reached the highest values. Fourier transform infrared spectroscopy (FTIR) results further revealed that the mechanism by which TGase and CS enhance the properties of TMP gels lies in the synergistic effect between the covalent isopeptide bonds catalyzed by TGase and the noncovalent interactions strengthened by CS. This synergistic effect induces an ordered transition in the secondary structure of proteins, resulting in the formation of a denser, more stable, and more regularly arranged gel network structure. In conclusion, this study elucidated the molecular mechanism by which TGase and CS synergistically drive the reconfiguration of the TMP gel network, and clarified the intrinsic relationship between performance enhancement and structural evolution. This provides a solid theoretical basis for the texture optimization, performance regulation, and industrial application of insect-based functional gels.