The indiscriminate use of packaging materials derived from petroleum has led to a large build-up of plastic in landfills and oceans, as these materials have low decomposition and are less recyclable. To alleviate 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 color, taste, smell and texture.
An example is a film made of a compound derived from limonene, the main component of citrus fruit peel, and chitosan, a biopolymer derived from chitin present in the exoskeletons of crustaceans.
The film was created by a research group in the state of São Paulo, Brazil, made up of scientists from the Department of Materials Engineering and Bioprocesses of the State University of Campinas’s School of Chemical Engineering (FEQ-UNICAMP) and the Institute’s Packaging Technology Center of Food. Technology (ITAL) of the São Paulo State Department of Agriculture and Supply, also in Campinas.
The results of the research are reported in an article published in Food Packaging and Shelf Life.
“We are focusing on limonene because Brazil is one of the largest producers of oranges in the world [if not the largest] and São Paulo is the leading orange-producing state,” said Roniérik Pioli Vieira, last author of the article and a professor at FEQ-UNICAMP.
Limonene has previously been used in food packaging film to improve preservation thanks to its antioxidant and anti-microbial action, but its performance has been degraded due to volatility and instability during the packaging manufacturing process, even on a laboratory scale.
This is one of the obstacles to the use of bioactive compounds in commercial packaging. It is often produced in processes involving high temperatures and high shear rates due to cutting or forming. Bioactive additives are easily degraded by 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 stable,” Vieira said.
The researchers chose chitosan for the film matrix because it is a polymer of natural origin and has well-known antioxidant and anti-microbial properties. Their hypothesis was that combining the two materials would create a film with improved bioactive properties.
In the laboratory, scientists compared films containing limonene and poly(limonene) in different proportions to meet the challenge of finding a way to combine them with chitosan, because theoretically they do not mix. The researchers chose polymerization, a process in which polymers are made from small organic molecules.
In this case, they use a compound with polar chemical functions to initiate the reaction and to increase the interaction between the additive and the polymer matrix. They then analyzed the resulting film to assess properties such as antioxidant capacity, vapor and water protection, and resistance to high temperatures.
The results were very satisfactory. “Films with poly(limonene) additive outperform those with limonene, especially in terms of antioxidant activity, which is twice as strong,” Vieira said. The substance has also been satisfactory as an ultraviolet radiation blocker and has been found to be unstable, 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 the chitosan-based plastic is not yet produced on a large enough scale to be competitive, but also because the poly(limonene) production process needs to be optimized to improve the yield and can be tested during the production of commercial packaging.
“Our group is working on it. We are investigating other applications of poly(limonene) in the biomedical field, for example. We are trying to show the multifunctionality of this additive, whose sources are renewable,” said Vieira.
Sayeny de Ávila Gonçalves et al, Poly(limonene): A novel renewable oligomeric antioxidant and UV-light blocking additive for chitosan-based films, Food Packaging and Shelf Life (2023). DOI: 10.1016/j.fpsl.2023.101085
Citation: Research team creates biodegradable film that keeps food fresher for longer (2023, July 17) retrieved on July 17, 2023 from https://phys.org/news/2023-07- group-biodegradable-food-fresh-longer.html
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