The careless use of petroleum-based packaging materials has resulted in a large amount of plastic in the mud and oceans, as these materials have low biodegradability and are rarely reused. In order to reduce this problem and meet the demand for products that are safe for human health and the environment, food companies are investing in the implementation of other storage methods that preserve health and organoleptic features such as color, taste, aroma and texture.
An example is a film made of a group derived from limonene, the main component of the peel of citrus fruits, and chitosan, a biopolymer derived from chitin present in the exoskeletons of crustaceans.
The film was created by a research team in the state of São Paulo, Brazil, which includes scientists in the Department of Technology 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, and in Campinas.
The results of this research are described in an article published in Food Packaging and Shelf Life.
“We thought a lot about limonene because Brazil is one of the countries that grow oranges the most in the world [if not the largest] and São Paulo is the leading country in the production of oranges,” said Roniérik Pioli Vieira, the last author of the article and a professor at FEQ-UNICAMP.
Limonene has long been used in food packaging to improve preservation due to its antioxidant and anti-microbial action, but its performance is hampered by instability and instability in packaging, even at the laboratory level.
This is one of the limitations of using bioactive compounds in commercial production. They are often produced in processes that involve high temperatures and high shear rates due to cutting or forming. Bioactive compounds are easily degraded in these processes.
“To solve this problem, we came up with the idea of using a derivative of limonene called poly(limonene), which is not volatile or unstable,” said Vieira.
The researchers chose chitosan for the film matrix because it is a natural polymer and has well-known antioxidant and anti-microbial properties. Their idea was that combining these two materials would create a film with a visual effect.
In the laboratory, scientists compared films with limonene and poly(limonene) in different ways to solve the problem of finding a way to combine them with chitosan, since they are known to be incompatible. The researchers chose polymerization, a process in which polymers are made from small molecules.
For this reason, they used a compound that contains polar compounds to initiate the reaction and increase the connection between the additive and the polymer matrix. They then analyzed the film for properties such as antioxidant power, light and water vapor protection, and resistance to high temperatures.
The results were very satisfying. “Films with poly(limonene) additives outperformed those with limonene, especially in terms of antioxidant, which was twice as strong,” said Vieira. The material also performed well as an ultraviolet barrier and was found not to vibrate, which makes it suitable for the production of large CDs, where damage is more difficult.
These films are not yet available for use by manufacturers, mainly because chitosan-based plastic has not yet been produced on a large enough scale to compete, and because the poly(limonene) process must be optimized for high yield and quality. tested during the production of commercial products.
“Our group is working on this. We have investigated other uses of poly(limonene) in the biomedical field, for example. We are trying to show the multifunctionality of this additive, whose origin is only increasing,” said Vieira.
More information:
Sayeny de Ávila Gonçalves et al, Poly(limonene): 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