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 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 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 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 65% lower carbon footprint than conventional plastic packaging. The synergistic action of Bi₂O₃ nanoparticles and chitosan matrix exhibits improved mechanical strength, enhanced barrier properties, and sustained antimicrobial activities, demonstrating excellent potential for food packaging applications.