A research team has developed a biodegradable active film from rapeseed processing residues that could offer a sustainable alternative to conventional plastic packaging. The material, described in a study published in Food Quality and Safety, combines chitosan with phenolic extracts from rapeseed cake, flowers, stems, and leaves, along with biosynthesized silver nanoparticles (AgNPs). This combination strengthens the film, improves resistance to water, oxygen, and UV light, and adds antioxidant and antimicrobial properties.
The study, conducted by researchers from Dalian Polytechnic University and INNOBIO Corporation Limited, addresses the dual challenges of food waste and plastic pollution. Conventional packaging protects food but persists in the environment, while bio-based films often lack the mechanical strength and barrier properties needed for demanding preservation conditions. Rapeseed production generates large amounts of underused byproducts rich in cellulose, polyphenols, and flavonoids. By extracting these compounds and using them to synthesize silver nanoparticles, the team created a composite film that outperforms pure chitosan in several key aspects.
The films showed significant improvements in mechanical properties, with tensile strength increasing from 8.1 to 17.0 MPa and elongation at break rising from 20.7% to 31.5%. The water contact angle increased from 55.7° to 87.2°, indicating better water resistance. The flower-based film exhibited the strongest antioxidant activity, scavenging 89.7% of DPPH radicals and 62.3% of ABTS radicals. The rapeseed-cake film inhibited the growth of Escherichia coli and Staphylococcus aureus.
In storage tests, the films slowed quality deterioration in cherry tomatoes and enoki mushrooms. Coated tomatoes retained more weight, ascorbic acid, and titratable acidity, while packaged mushrooms showed less browning and microbial growth. The films also degraded completely in soil within 21 days without negatively affecting bok choy growth, supporting their potential for circular packaging systems.
The authors emphasize that crop residues can do more than replace part of a packaging material; their natural chemistry can help the package actively protect food. The produce trials demonstrate the material's effectiveness on highly perishable foods with different spoilage patterns. The films could be used as coatings, wraps, or liners for fresh produce, reducing reliance on persistent plastics and creating new value streams for agricultural residues.
However, the researchers note that commercial application requires further work. Scalable manufacturing, cost and sensory assessments, standardized food-contact testing, and trials under realistic transport and storage conditions are needed. While EDS found no detectable silver on tested tomatoes, the study describes this as preliminary evidence. Future research should use quantitative methods such as ICP-MS to assess long-term exposure and evaluate degradation across diverse environments.
The study is published with DOI 10.1093/fqsafe/fyag032 and was funded by the Basic Scientific Research Fund of Liaoning Provincial Education Department and the China Postdoctoral Science Foundation.
