Abstract: A composite film was developed using pea protein (PP) as the film-forming substrate, chitosan (CS) as the film-modifying material, chlorogenic acid (CA) as the functional component, tyrosinase (Tyr) as the crosslinking agent, and glycerol as the plasticizer. The physical parameters and microstructure of the PP-CA-CS film were determined. The aim was to explore the effects of PP-to-CS ratio and the concentrations of CA and Tyr on the structure and properties of the composite film and to study the interaction between its components. The results showed that the antioxidant potential and mechanical properties of the composite film were significantly improved after the addition of CA, and Tyr catalyzed the covalent cross-linking of CA with PP and CS. With the addition of CA and Tyr, the cross-linking degree and mechanical properties were improved. At a PP-to-CS ratio of 1:1, at 20 mmol/L CA concentration and at 18 U/mL Tyr concentration, the composite film had the best mechanical properties, antioxidant properties and water vapor barrier properties. In addition, the tensile strength of the film was 130.78 MPa, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity was 69.05%. Compared with pure PP-CS film, the mechanical properties of the PP-CA-CS composite film were increased by 3.6 times, the antioxidant potential was increased by 3.2 times, and the water vapor permeability was decreased by 8%. The results of scanning electron microscopy (SEM) showed that the PP-CA-CS composite film was smooth and compact, so it had high water vapor barrier performance. No new functional groups were generated in the film formation process as demonstrated by infrared spectral analysis. Therefore, this study provides a new idea for researchers in the field of new food packaging, and offers data and theoretical support for the development of edible films.

Key words: pea protein; chlorogenic acid; chitosan; tyrosinase; edible films