From Brassica napus L. Waste to Active Packaging: Eco-friendly Composite Films with Built-in Antioxidant and Antimicrobial Properties for Fresh Preservation

Although chitosan (CS)-based biomass packaging materials show promise for food preservation, their practical application is limited by poor mechanical strength, UV resistance, antioxidant capacity, and high water solubility. This study developed high-performance CS composite films incorporating phenolic extracts of rapeseed processing byproducts (rapeseed cake, flower, stem, and leaf) via biosynthesis technology. Compared with the pure CS film, the optimized composite film (CBR-Ag) exhibited markedly improved performance. Specifically, its tensile strength increased from 8.1 ± 0.3 to 17.0 ± 0.5 MPa (an increase of 110%). Elongation at break rose from 20.7% ± 1.2% to 31.5% ± 1.8%. The film demonstrated exceptional UV-blocking, with transmittance at 280 nm reduced to less than 1%. Barrier properties were significantly enhanced: water vapor permeability decreased by 42% (from 2.72 × 10−10 to 1.58 × 10−10 g/(mm·Pa·h)), and oxygen permeability was lowered by 35%. Antioxidant activity, measured via DPPH and ABTS assays, reached 89.7% ± 3.0% and 62.3% ± 2.7% free radical scavenging rates, respectively. In practical preservation tests conducted at 25 °C and 50% relative humidity, cherry tomatoes coated with the CBR-Ag film retained 83.6% of their initial weight after 12 d of storage, compared with 68.2% for uncoated controls, while also exhibiting significantly higher firmness, titratable acidity, and ascorbic acid content. This study establishes an innovative strategy for the comprehensive utilization of rapeseed processing byproducts while demonstrating the practical efficacy of the developed bioactive packaging system in extending food shelf life.