Abstract: Sodium alginate (SA) and κ-carrageenan (κ-C) are often used as natural non-toxic materials in edible packaging films due to their good film-forming ability. However, the formed polysaccharide films have some disadvantages, such as strong hydrophilicity, poor mechanical properties and low antioxidant activity. This study aimed to enhance the packaging performance of natural edible composite films and impart antioxidant activity to it by adding egg white powder (EWP) and apple polyphenols (AP) into SA/κ-C-based film-forming matrix with calcium lactate added as a cross-linking agent. The film was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron microscopy (SEM) and ultraviolet (UV) spectroscopy, and the interactions among the components were analyzed. The edible composite film was applied to the preservation of cashew nuts. The results indicated that the composite edible film with AP and EWP showed good packaging performance and antioxidant properties. The mechanical properties and barrier properties of the edible film were significantly improved by Ca2+ cross-linking. With the addition of egg white powder, the elongation at break of the film increased from 7.99% to 20.81%, the water vapor permeability decreased by 28.84%, and the oxygen permeability decreased by 27.07%. AP increased the tensile strength of the film from 18.58 MPa to 30.23 MPa, decreased the water vapor permeability and oxygen permeability by 42.35% and 34.13%, respectively, and significantly improved the light barrier performance. The AP/EWP/SA/κ-C edible film could inhibit the increase in the water activity, water content, peroxide value and acid value of cashew nuts during storage, thereby effectively inhibiting the oxidative rancidity of cashew nuts. The findings of this study can provide a reference for the preparation and application of polysaccharide/protein-based edible composite packaging films.

Key words: egg white, apple polyphenol, sodium alginate, κ-carrageenan, edible films