A new material made from substances common in crab shells and tree fibers could replace the flexible plastic packaging used to keep food fresh.
Researchers from the Georgia Institute of Technology sprayed multiple, alternating layers of chitin—a fibrous substance consisting of polysaccharides that is present in shellfish, insects and fungi—and cellulose, a biopolymer present in plants and trees, to form a flexible film that can compete with plastic packaging film.
“The main benchmark that we compare it to is PET, or polyethylene terephthalate, one of the most common petroleum-based materials in the transparent packaging you see in vending machines and soft drink bottles,” J. Carson Meredith, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering, said in a statement. “Our material showed up to a 67 percent reduction in oxygen permeability over some forms of PET, which means it could in theory keep foods fresher longer.”
The researchers suspended the cellulose and chitin nanofibers in water and then sprayed them onto a surface in alternating layers. After the material is fully dried, it is flexible, strong, transparent and compostable.
“We had been looking at cellulose nanocrystals for several years and exploring ways to improve those for use in lightweight composites as well as food packaging, because of the huge market opportunity for renewable and compostable packaging, and how important food packaging overall is going to be as the population continues to grow,” Meredith said. “We recognized that because the chitin nanofibers are positively charged, and the cellulose nanocrystals are negatively charged, they might work well as alternating layers in coatings because they would form a nice interface between them.”
Packaging used to preserve food must prevent oxygen from passing through. However, the new material is an improvement as a gas barrier over conventional plastic packaging because of the crystalline structure of the film.
“It’s difficult for a gas molecule to penetrate a solid crystal, because it has to disrupt the crystal structure,” Meredith said. “Something like PET on the other hand has a significant amount of amorphous or non-crystalline content, so there are more paths easier for a small gas molecule to find its way through.”
While the material could one day be a viable replacement for petroleum-based materials, the researchers still need to develop a manufacturing process that maximizes the economy of scales. Also, unlike industrial processes to mass produce cellulose, methods to produce chitin are still in their infancy. More research is also needed to improve the material’s ability to block water vapor.
The study was published in ACS Sustainable Chemistry & Engineering.