Modification of nanocellulose filler via amination and subsequent grafting of gallic acid for enhancing the performance of biodegradable soy protein films in banana packaging

The excessive use of petroleum-based packaging necessitates the need for sustainable, biodegradable alternatives. This study developed a high-performance active packaging film by incorporating chemically modified cellulose nanocrystals (CNCs) into a soy protein isolate (SPI) matrix. CNCs were functionalized via silanization with 3-aminopropyltriethoxysilane (APTES) followed by covalent gallic acid grafting. Compared to glycerol-plasticized SPI, the composite films showed significantly enhanced mechanical strength (237.3% increase in tensile strength, from 2.17 to 7.32 MPa), improved water vapor barrier (30.16% reduction in permeability), nearly 100% UV blocking at 200–350 nm, antioxidant activity (12.4% DPPH scavenging), and antibacterial properties. In a 7-day banana preservation test, the optimized film effectively delayed weight loss, softening, and browning while remaining biodegradable, showing visible degradation within 20 days in soil. This work demonstrates a feasible interfacial design strategy for developing multifunctional SPI-based nanocomposite films with high potential for fresh-keeping packaging of perishable fruits such as bananas.