A research team has developed a biodegradable active film from rapeseed processing residues, offering a sustainable alternative to petroleum-based packaging while extending the shelf life of fresh produce. The innovation, reported in the journal Food Quality and Safety, combines chitosan with phenolic extracts from rapeseed cake, flowers, stems, and leaves, along with biosynthesized silver nanoparticles, to create a material that is stronger, more water-resistant, and capable of actively preserving food.
The study addresses a critical challenge in food packaging: conventional plastics protect products from moisture, oxygen, and microbes but persist in the environment for centuries. While bio-based films offer a renewable alternative, pure chitosan films often lack the mechanical strength and barrier properties needed for demanding applications. The team, from Dalian Polytechnic University and INNOBIO Corporation Limited, sought to enhance chitosan films using the natural chemistry of rapeseed byproducts, which are rich in cellulose, polyphenols, and flavonoids.
The researchers extracted bioactive compounds from rapeseed cake, flowers, stems, and leaves, and used them to synthesize silver nanoparticles averaging about 60 nanometers. These were then incorporated into chitosan film-forming solutions to create composite films. Testing showed that the rapeseed-cake extract–silver nanoparticle film had tensile strength increased from 8.1 to 17.0 MPa and elongation at break from 20.7% to 31.5%, compared to pure chitosan. The water contact angle rose from 55.7° to 87.2°, indicating improved water resistance. The flower-based film exhibited the strongest antioxidant activity, with 89.7% scavenging in the DPPH assay and 62.3% in the ABTS assay, while the rapeseed-cake film inhibited Escherichia coli and Staphylococcus aureus.
In storage tests, cherry tomatoes coated with the film retained more weight, ascorbic acid, and titratable acidity, while enoki mushrooms showed less browning and microbial deterioration. The films also degraded completely in soil within 21 days without adversely affecting bok choy growth, supporting a circular packaging system.
The study's significance lies in demonstrating that agricultural residues can be transformed into high-value packaging materials that actively protect food. The authors emphasize that the produce trials are particularly important because they show real-world performance on perishable foods with different spoilage patterns. The films could be used as coatings, wraps, or liners for fresh produce, offering a way to reduce dependence on persistent plastics while creating new value from rapeseed byproducts.
However, commercial adoption will require addressing scalability, cost, sensory impacts, and standardized food-contact testing. The study notes that energy-dispersive X-ray spectroscopy found no detectable silver on tested tomatoes, but this is preliminary; future work should use quantitative methods like ICP-MS and evaluate degradation in diverse environments.
The research was funded by the Basic Scientific Research Fund of Liaoning Provincial Education Department and the China Postdoctoral Science Foundation. The full study is available at https://doi.org/10.1093/fqsafe/fyag032.
