Improving the comprehensive properties of gelatin films by transglutaminase and chitosan

Biodegradable gelatin films have attracted much attention as food packaging. However, the disadvantages of these films, such as strong hydrophilicity, low mechanical strength, and thermal stability, greatly limit their applications. In this study, transglutaminase (TGase) and chitosan were adopted into gelatin films to improve the comprehensive properties of gelatin films, taking advantage of their covalent and non-covalent interactions with gelatin, and the effects of chitosan with the concentration of 0.4–0.8 % and TGase with the concentration of 0.1–0.3 % on the physicochemical properties of the gelatin-based films were investigated. Results showed that incorporating chitosan and TGase significantly reduced the films' UV light transmission and hydrophilicity, manifesting as a decrease in water vapor transmittance from 2.12 (g·mm)/m2·h·kPa to 1.35 (g·mm)/m2·h·kPa, a decrease in water solubility from 74.03 % to 55.40 %, and an increase in water contact angle from 97.82° to 108.19°. In addition, the films' mechanical strength improved from 2.60 MPa to 9.25 MPa and melting temperature improved from 94.43 °C to 113.23 °C after adding chitosan and TGase. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) revealed the covalent and non-covalent crosslinking effects of TGase and chitosan on gelatin. Overall, the comprehensive performance of gelatin film after adding chitosan and TGase has been improved.