Antimicrobial Bi₂O₃–Chitosan Nanocomposite Films for Sustainable Food Packaging: Enhanced Barrier Properties and Preservation Performance ^†

Demand for sustainable packaging in the global market has led to the development of environmentally friendly alternatives to conventional plastic materials. This study investigates the synthesis and characterization of Bi₂O₃-loaded chitosan nanocomposite films as advanced eco-friendly packaging materials with enhanced antimicrobial and barrier properties.

Bi₂O₃ nanoparticles (20–50 nm) were produced using controlled precipitation and then embedded in a high-molecular-weight chitosan matrix at 1, 3, 5, and 7 wt% using solution casting coupled with probe sonication. Plasticization of films was achieved using glycerol (30% w/w).

Detailed characterization confirmed an α-Bi₂O₃ crystalline phase with homogeneous nanoparticle dispersion throughout the chitosan matrix. The nanocomposite films demonstrated excellent broad-spectrum antimicrobial activity, achieving 99.9% elimination of E. coli and S. aureus within 4 h and complete elimination within 8 h. Growth of A. niger was completely inhibited after 7 days, with reasonable antibacterial activity being retained after 30 days under ambient conditions.

Practical food preservation trials using fresh strawberries showed superior performance compared to conventional polyethylene packaging, with 60% less weight loss (8.2% vs. 20.5%), reduced firmness loss (15% vs. 45%), and extended shelf life by 8 days. Microbial counts were significantly reduced, and nutritional quality was better preserved with 23% higher ascorbic acid retention.

Biodegradation studies demonstrated complete degradation within 45 days under composting conditions, with life cycle assessment indicating a 65% lower carbon footprint than conventional plastic packaging. The synergistic action of Bi₂O₃ nanoparticles and a chitosan matrix exhibits improved mechanical strength, enhanced barrier properties, and sustained antimicrobial activities, demonstrating excellent potential for food packaging applications.