Physical and Antioxidant Properties of Edible Chitosan Ascorbate Films

Chitosan ascorbates with different substitution degrees were synthesized on the basis of salification of chitosan and ascorbic acid at various molar ratios in water and were successfully used to prepare antioxidative films by casting for the first time. Fourier transform infrared and ¹H nuclear magnetic resonance spectra recorded the structural characteristics of all chitosan ascorbates; meanwhile, physicochemical property and antioxidant activity of the produced chitosan ascorbate films were characterized, with chitosan acetate film serving as the control, and these properties were also measured for comparison. The results revealed that salification of chitosan with ascorbic acid not only improved the total color difference, chroma, opacity, capacity for blocking ultraviolet-visible light, and water solubility of chitosan-based films but also decreased water content, swelling degree, and water vapor permeability compared to chitosan acetate film. Also, as was expected, the antioxidant activity assays showed that incorporation of ascorbate into the chitosan matrix effectively enhanced the scavenging activity against the DPPH radical and reducing power. Cs₂Vc₈ and Cs₂Vc₆ especially exhibited the strongest scavenging capacities against the DPPH radical (EC₅₀ < 0.025 mg/mL). These findings offered a suggestion that the prepared chitosan ascorbate films can be applied as novel green oxidation-resistant materials in the food packaging industry.