Structural properties of films and rheology of film-forming solutions of chitosan gallate for food packaging

• The grafting reaction was accompanied with a degradation of the CS molecule.
• The CG film-forming solution grafted at a lower GA value behaved like an network system with a more elastic behavior.
• The increasing of GA grafting onto the CS chain led to a reduction of TS, E and WVP in the corresponding films.
• The antioxidant and antimicrobial activities of CG film increased with DS.
• The microstructure of the film was closely related to the observed film properties.

The chitosan gallates (CG) were obtained by free-radical-initiated grafting of gallic acid (GA) onto chitosan (CS) in this work. The chemical structures of the CG were corroborated by UV–vis, GPC and 1H NMR analysis. The grafting reaction was accompanied with a degradation of the CS molecule. The shear-thinning flow behavior of CG film-forming solutions (CG FFS) decreased with the grafting amount of GA into CS chain, while the CG FFS grafted at a lower GA value behaved like a networks containing entangled or cross-linked polymer chains with a more elastic behavior. The increasing of GA grafting onto the CS chain led to a reduction of tensile strength, elongation at break and water resistance in the corresponding films, but increases in the antioxidant and antimicrobial activities were observed. The microstructure of the film was investigated using scanning electron and atomic force microscope, and the results were closely related to the observed film properties.