The covalent crosslinking of dialdehyde glucomannan and the inclusion of tannic acid synergistically improved physicochemical and functional properties of gelatin films

The recent awareness of food safety has increased the attractiveness of natural polymer packaging film. However, the weak physicochemical properties have greatly restricted their practical applications. Therefore, in this work, gelatin was crosslinked by dialdehyde glucomannan, and tannic acid was introduced to enhance the properties of the gelatin-based films. The heat treatment enhanced the covalent crosslinking between dialdehyde glucomannan and gelatin. The tannic acid introduction resulted in darkened color, and enhanced UV blocking property and thermal stability of the films. And the novel gelatin films showed smooth surface and cross-section, enhanced mechanical properties, and reduced water vapor permeability. In addition, the enhanced crosslinking eliminated the increased swelling caused by tannic acid. More notably, the films contained a distinct antioxidant capacity and a significant inhibitory effect on S. aureus. This study demonstrated that tannic acid and the enhanced covalent crosslinking could synergistically improve the properties of the gelatin films for food packaging.