Researchers have developed a biodegradable active film from rapeseed processing residues that could reduce reliance on petroleum-based packaging while improving food preservation. The material, reported in Food Quality and Safety, combines chitosan with phenolic extracts from rapeseed cake, flowers, stems, and leaves, and biosynthesized silver nanoparticles (AgNPs). This composite strengthens the film, improves resistance to water, oxygen, and UV light, and adds antioxidant and antimicrobial properties.
The study, conducted by scientists from Dalian Polytechnic University and INNOBIO Corporation Limited, addresses the limitations of conventional plastics, which persist in the environment after disposal. Bio-based films offer a renewable alternative, but pure chitosan films often lack the mechanical strength and barrier performance needed for demanding preservation conditions. The team aimed to create a multifunctional packaging material that actively protects food while converting agricultural residues into higher-value products.
Using extracts from rapeseed byproducts, the researchers synthesized silver nanoparticles averaging about 60 nanometers under mild conditions, then embedded these components into a chitosan matrix. The resulting films exhibited a smooth, compact structure with well-dispersed silver. Compared to pure chitosan, the composite film containing rapeseed cake extract and silver nanoparticles showed a tensile strength increase from 8.1 to 17.0 MPa and elongation at break from 20.7% to 31.5%. The water contact angle rose from 55.7° to 87.2°, indicating improved water resistance.
The films also demonstrated strong antioxidant activity, with the flower-based film achieving 89.7% scavenging in the DPPH assay and 62.3% in the ABTS assay. The rapeseed cake film inhibited Escherichia coli and Staphylococcus aureus. In storage tests, coated cherry tomatoes retained more weight, ascorbic acid, and titratable acidity, while packaged enoki mushrooms showed less browning and microbial deterioration. The films fully degraded in soil within 21 days without significantly affecting bok choy growth.
According to the authors, the key significance is that crop residues can do more than replace part of a packaging material; their natural chemistry can actively protect food. By pairing rapeseed phenolics with biosynthesized AgNPs, the team created a film that is stronger, less vulnerable to moisture, and better able to slow oxidation and microbial growth. The produce trials are particularly important as they demonstrate practical application on perishable foods with different spoilage patterns.
The films could be used as coatings, wraps, or liners for fresh produce and other foods susceptible to dehydration, oxidation, browning, and microbial spoilage. This approach also creates new value streams for rapeseed-processing residues while reducing dependence on persistent plastics. However, commercial translation requires scalable manufacturing, cost and sensory assessments, standardized food-contact testing, and trials under realistic transport and storage conditions. The study noted that EDS found no detectable silver on tested tomatoes, but this is preliminary; future work should use quantitative methods like ICP-MS and evaluate long-term exposure and 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.
