Physicochemical Reinforcement of Hydrophilic Gelatin Films by Fibroin Nanofibrils Prepared via Cellulose-Assisted Self-Assembly

This study developed cellulose-assisted silk nanofibrils through a templated cellulose regeneration process. During cellulose dissolution and regeneration, the structure of silk fibroin transitioned into β-sheet, facilitating its self-assembly into nanofibrils. These cellulose-assisted fibroin nanofibrils exhibited excellent dispersion stability and optical properties. When incorporated as nanofillers in gelatin based composite films, these nanofibrils, unlike cellulose nanofibrils, directly participated in the fructose-mediated Maillard reaction. This led to enhanced structural densification and functionalization. The combination of the Maillard reaction and the cellulose-assisted fibroin nanofibrils had a synergistic effect, resulting in significant improvements in mechanical properties, including tensile strength (17.68 ± 0.39 MPa), Young's modulus (476.59 ± 1.39 MPa), and tensile strain (442.45% ± 4.93%). Moreover, the film exhibited strong ultraviolet-blocking capabilities, enhanced moisture barrier properties, and excellent antioxidant activity. As a result, the cross-linked cellulose-assisted fibroin nanofibril reinforced gelatin composite film demonstrated excellent performance as a food packaging material, effectively inhibiting bacterial growth and reducing weight loss. These findings suggest that silk-based nanofibrils capable of participating in chemical cross-linking can serve as robust physicochemical reinforcing agents and functional fillers for protein-based edible packaging films.