Effects of plasticizer type and concentration on rheological, physico-mechanical and structural properties of chitosan/zein film

The purpose of this study was to evaluate the effect of plasticizer type (glycerol, PEG-400, and sorbitol) and concentration (0%, 15%, 30% and 45%, w/w dry polymer weight) on rheological and physico-mechanical and structural properties of chitosan/zein blend film. Based on the analysis of rheological properties of chitosan/zein film-forming solutions, all film-forming solutions exhibited non-Newtonian behavior. The flow index of film-forming solution increased and apparent viscosity decreased with the increase of plasticizer concentration. The storage modulus (G′) and the loss modulus (G″) decreased when plasticizer was added. The permeability of films increased significantly with the increase of plasticizer concentration, but the C/Z-P film (plasticized chitosan/zein film with PEG-400) had better barrier performance compared with the other two. The C/Z-P film had better mechanical properties and light transmission. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed chitosan and zein had good compatibility due to the addition of the plasticizer, and crystallinity decreased with the increase of plasticizer concentration.