Effect of α-tocopherol antioxidant on rheological and physicochemical properties of chitosan/zein edible films

Abstract

Edible films of chitosan/zein/α-tocopherol were fabricated by solution casting process. The effect of α-tocopherol (0 g/100 mL, 0.5 g/100 mL, 1 g/100 mL, 1.5 g/100 mL and 2.0 g/100 mL) on rheological properties, particle size and zeta potential of film-forming solutions, as well as physicochemical and structural characterization of films was investigated. Rheological properties suggested that solutions exhibited a shear-thinning and typical entangle polymers solutions behavior. G′ and G" of film-forming solutions had crossover points at the lowest frequency when the α-tocopherol concentration was 1 g/100 mL. The zeta potential increased from +26.023 to +37.187 mV, which revealed that α-tocopherol could improve the stability of solutions. The PDI decreased from 0.354 to 0.222, indicating that the film-forming solutions became uniform. The addition of α-tocopherol resulted in low water vapor permeability and excellent opacity. The lowest water vapor permeability of film was 0.944 kg m·m−2·s−1·Pa−1 and the maximum opacity of film was 12.601. It was observed that the highest value of DPPH radical scavenging was 97.66% when the α-tocopherol concentration was 1 g/100 mL. SEM images suggested that α-tocopherol exhibited better dispersion when the α-tocopherol concentration was 1 g/100 mL. The X-ray diffraction demonstrated that α-tocopherol, zein and chitosan had good compatibility.