Abstract:Starch films, which were prepared using starch composites that had been modified through enzymatic debranching and etherification processes, were further enhanced by the addition of citric acid and glycerin and their structural characteristics and relevant mechanisms were investigated. From the process optimization experiments, a 3% starch-based material concentration, 30% glycerin content, 10% citric acid content, and 95°C processing temperature were found to result in a starch film with the best physicochemical characteristics. The film had a tensile strength of 4.11 MPa, an elongation at break of 38% (a 45% increase over the non-enhanced film), and a water vapor permeability coefficient of 0.51 g·mm/(m2·h·kPa) (a 39% decrease over the non-enhanced film). Structural analysis revealed the starch film to have a relatively open crosslinked network structure, in which the starch chain was preferentially combined with the ester formed by citric acid and glycerin. Additionally, the network structure was weakened by the hydrolysis effects of citric acid. Therefore, the addition of citric acid can effectively improve the mechanical and barrier properties of modified starch films, enabling the preparation of composite films with excellent overall performance. The results of this study provide a scientific basis for future studies on the applications of starch-based food packaging materials.
