The global plastic crisis has been an escalating concern due to the slow degradation and inadequate recycling of petroleum-based packaging materials. As a result, an alarming accumulation of plastic waste has inundated landfills and polluted our oceans.
Acknowledging the issue and the increasing demand for environment-friendly and health-conscious products, the food industry has set its sights on developing sustainable packaging alternatives that not only preserve nutritional quality but also uphold organoleptic traits such as color, taste, smell, and texture.
A groundbreaking step in this direction comes in the form of a film created from a unique compound derived from limonene, the primary component found in citrus fruit peels, combined with chitosan, a biopolymer sourced from the chitin present in the exoskeletons of crustaceans.
The innovation emerged from a collaborative effort by a research group based in São Paulo state, Brazil. Comprising scientists from the Department of Materials Engineering and Bioprocesses at the State University of Campinas’s School of Chemical Engineering (FEQ-UNICAMP) and the Packaging Technology Center at the Institute of Food Technology (ITAL) of the São Paulo State Department of Agriculture and Supply, the team achieved remarkable results, which have been reported in the esteemed journal Food Packaging and Shelf Life.
Roniérik Pioli Vieira, a professor at FEQ-UNICAMP and the last author of the article, explained the motivation behind focusing on limonene, stating, "Brazil stands among the world’s largest producers of oranges, and São Paulo leads the pack in orange production." Limonene had previously been utilized in food packaging films due to its antioxidant and antimicrobial properties. However, its volatility and instability during the packaging manufacturing process hindered its performance, even on a laboratory scale.
One of the major challenges in incorporating bioactive compounds into commercial packaging is their vulnerability to degradation during production, which often involves high temperatures and shear rates. To overcome this limitation, the research team turned to poly(limonene), a limonene derivative known for its non-volatile and stable nature.
The scientists elected to use chitosan as the film matrix, owing to its natural origin and well-established antioxidant and antimicrobial attributes. Their hypothesis was that the combination of these two materials would result in a film with enhanced bioactive properties.
In their laboratory experiments, the researchers compared films containing limonene and poly(limonene) in varying proportions, striving to overcome the challenge of blending them with chitosan, which are theoretically incompatible. To tackle this hurdle, they opted for polymerization, a process that transforms smaller organic molecules into polymers. By utilizing a compound with polar chemical functions to initiate the reaction and enhance the interaction between the additive and the polymer matrix, they achieved promising results.
The analysis of the resulting film demonstrated outstanding properties, including superior antioxidant capacity- almost twice as potent as limonene alone. Additionally, the substance performed remarkably as an ultraviolet radiation blocker and was proven to be non-volatile, making it suitable for large-scale packaging production under more demanding processing conditions.
Despite these promising outcomes, limonene and chitosan-based films are not yet readily available for manufacturers. The primary roadblock lies in the limited-scale production of chitosan-based plastic, which currently hampers its competitiveness. Furthermore, the poly(limonene) production process requires optimization to improve yields and undergo testing during commercial packaging manufacturing.
Undeterred, the research group is actively working to address these challenges. Exploring other potential applications of poly(limonene) in the biomedical field and highlighting the additive's multifunctionality from renewable sources are among their ongoing efforts.
