Characterization of chitosan–oleic acid composite films

Edible films based on high molecular weight chitosan (CH) and different concentrations of oleic acid (OA) were prepared. Film-forming dispersions (FFD) were characterized in terms of rheological properties, surface tension, particle size distribution and ζ-potential. In order to study the impact of the incorporation of OA into the CH matrix, the water sorption isotherms, water vapour permeability (WVP), mechanical properties, and optical properties of the dry films were evaluated. Results showed that the increase in OA promoted changes in the size and surface charge of the FFD particles, which had an impact on the rheological properties of the FFD. As regards the film properties, the higher the OA content, the lower the WVP and the moisture sorption capacity. In general, the addition of OA into the CH matrix leads to a significant increase in gloss and translucency and a decrease in the tensile strength, elongation at break and elastic modulus of the composite films. The mechanical and optical properties of the films were related with their microstructure, which was observed by SEM.