Preparation of Highly Transparent, Mechanically Enhanced, Antioxidant, and Biodegradable SPI/OAG Films via Synergistic Schiff Base Chemistry and Hydrogen Bonding Interactions

Excessive use of nondegradable plastics has raised environmental concerns, promoting the development of high-performance and eco-friendly materials. Polysaccharides and proteins, which offer advantages such as affordability and biodegradability, have potential in packaging but are limited in barrier and mechanical properties. Herein, using 30% acetic acid as a solvent for soy protein isolate (SPI) and introducing oxidized arabinogalactan (OAG) into the system, highly transparent (90%) and ultraviolet-shielding SPI/OAG flexible films were successfully prepared via Schiff base chemical cross-linking and hydrogen bond interactions between the components. The synergistic cross-linking of SPI and OAG effectively increased mechanical strength (tensile strength of 6.93 MPa), improved oxygen and water vapor barrier properties, and reduced swelling in the SPI/OAG films. The films exhibited good antioxidant activity (81.75% for ABTS and 85.34% for DPPH), effectively retarded browning and weight loss of strawberry and apple pieces, and were biodegradable in soil. The prepared SPI/OAG films had advantages over existing SPI-based films, including a uniform structure, low oxygen permeability, and excellent sustainability. This research demonstrates that SPI/OAG cross-linked films have strong potential in biodegradable packaging and as a substitute for petroleum-based plastics.