Synergistic reinforcement of calcium cross-linked soy protein isolate/cellulose nanocrystal films with lignin-zinc oxide nanoparticles for active biodegradable fruit packaging

To address petroleum-based packaging pollution and postharvest food waste, developing biodegradable composite films with tailored physicochemical properties is highly desirable. Herein, a sustainable composite film comprising soy protein isolate (SPI), cellulose nanocrystals (CNCs), and lignin–zinc oxide nanoparticles (LZNPs) was fabricated via Ca²⁺-mediated ionic cross-linking and non-covalent interactions. The synergistic hydrogen bonding and ionic cross-linking formed a robust three-dimensional polymer network, significantly enhancing the tensile strength of the film and establishing excellent barrier properties against water vapor, oxygen, and carbon dioxide. Specifically, the LZNPs functionalized with phenolic hydroxyl groups and Zn²⁺ ions endowed the film with strong antioxidant activity (free-radical scavenging rates >70%) and potent antibacterial activity (nearly complete inhibition of the growth of both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus ). Consequently, this high-performance composite film effectively preserved bananas, plums, and cherry tomatoes, extending their shelf life for over 10 days. Moreover, the film exhibited excellent biosafety in seed germination assays and achieved complete soil biodegradation within 30 days. This work provides a promising strategy for developing biodegradable multifunctional packaging materials and demonstrates significant potential for advancing sustainable fruit preservation. Download: Download high-res image (240KB) Download: Download full-size image