The indiscriminate use of petroleum-derived packaging materials has led to a huge accumulation of plastics in landfills and at sea, as these materials are poorly degradable and not recycled to any significant extent. To mitigate this problem and meet the growing demand for products that are safe for human health and the environment, the food industry is investing in the development of more sustainable packaging alternatives that preserve nutritional quality as well as organoleptic characteristics such as colour, taste, smell, etc Texture.
One example is a film made from a compound made from limonene, the main component of citrus peel, and chitosan, a biopolymer derived from chitin found in crustacean exoskeletons.
The film was developed by a research group in the Brazilian state of São Paulo, composed of scientists from the Department of Materials Engineering and Bioprocesses at the School of Chemical Engineering, State University of Campinas (FEQ-UNICAMP) and the Packaging Technology Center at the Institute of Food Technology (ITAL) of the Ministry of Agriculture and Utilities of the State of São Paulo, also in Campinas.
The research results will be reported in an article published In Food packaging and shelf life.
“We focused on lime because Brazil is one of the world’s largest orange producers [ if not the largest ] and São Paulo is the leading orange producer,” he said Ronierik Pioli Vieira last author of the article and professor at FEQ-UNICAMP.
Limonene has previously been used in food packaging films to improve preservation due to its antioxidant and antimicrobial properties. However, its performance is hampered by volatility and instability during the packaging manufacturing process, even on a laboratory scale.
This is one of the barriers to using bioactive compounds in commercial packaging. It is often made in processes that require high temperatures and high shear rates when cutting or forming. Bioactive additives are easily broken down in these processes.
“To solve this problem, we came up with the idea of using a derivative of limonene called poly(limonene), which is neither volatile nor particularly unstable,” Vieira said.
Researchers chose chitosan as the film matrix because it is a naturally derived polymer and has known antioxidant and antimicrobial properties. Their hypothesis was that combining the two materials would create a film with enhanced bioactive properties.
In the lab, scientists compared films containing limonene and poly(limonene) in different proportions to meet the challenge of finding a way to combine them with chitosan, since theoretically they do not mix. The researchers opted for polymerization, a process that creates polymers from smaller organic molecules. In this case, they used a compound with polar chemical functions to start the reaction and increase the interaction between the additive and the polymer matrix. They then analyzed the resulting film to evaluate properties such as antioxidant capacity, light and water vapor protection, and resistance to high temperatures.
The results were highly satisfactory. “The films with the addition of poly(limonene) outperformed those with limonene, particularly in terms of antioxidant activity, which was about twice as potent,” said Vieira. The substance also showed a satisfactory effect as an ultraviolet ray blocker and proved to be non-volatile, making it suitable for large-scale production of packaging where the processing conditions are more severe.
The films are not yet available to manufacturers, mainly because chitosan-based plastic is not yet manufactured on a large enough scale to be competitive, but also because the poly(limonene) production process needs to be optimized to improve yields tested in the manufacture of commercial packaging.
“Our group is working on it. For example, we have explored other applications of poly(limonene) in the biomedical field. We are trying to demonstrate the multifunctionality of this additive, the origin of which is renewable,” said Vieira.
The study was funded by FAPESP through two projects (20/14837-3 And 21/04043-2).
About the Sao Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public body tasked with supporting scientific research in all fields of knowledge by awarding grants, fellowships and grants to researchers affiliated with higher education and research institutions in the Brazilian state of São Paulo. FAPESP recognizes that the best research is only possible by collaborating with the best researchers at the international level. Therefore, it has established partnerships with funding agencies, universities, private companies and research organizations in other countries that are known for the quality of their research, and encourages scientists funded by its grants to further expand their international collaborations. You can learn more about FAPESP at www.FAPESP.br/en and visit the FAPESP news agency at www.agencia.FAPESP.br/en to keep up to date with the latest scientific breakthroughs that FAPESP is helping to achieve through its numerous programs, awards and research centers. You can also subscribe to the FAPESP news agency at http://agencia.FAPESP.br/subscribe.