When it comes to keeping food fresh, plastic still tends to be the best method. Researchers from the Georgia Institute of Technology are trying to change this by changing the plastic used for preserving food, which requires packaging that keeps oxygen out. In a recent press release, the team of researchers announced the creation of a flexible film that uses multiple layers of chitin from crab shells and tree cellulose.
“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,” said J. Carson Meredith, Georgia Tech School of Chemical and Biomolecular Engineering professor. “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 focused on harnessing two of the most common substances on Earth to create the material. Cellulose is an insoluble biopolymer found in plant cell walls. Researchers have heavily been studying ways to use it at the nanolevel, including to strengthen wood. Chitin is a fibrous substance that has polysaccharides and is found in shellfish, insects and fungi. The shellfish food industry leaves behind a plentiful supply of chitin-rich byproducts. Both are renewable resources.
“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.
During their research, the team found that since chitin nanofibers are positively charged and cellulose nanocrystals are negatively charged, the two substances would make a great combo for a new material. The team developed a system to suspend the cellulose and chitin nanofibers in water and then sprayed it in layers. After drying, the result is a clear, durable material that is compostable. Its crystalline structure prevents oxygen from getting through, which is an enhancement on traditional plastic wrap.
“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 noncrystalline content, so there are more paths easier for a small gas molecule to find its way through.”
Although the new material has innumerable benefits, researchers aren’t quite done with their work. More research is needed to improve its ability to block water vapor. In addition, harvesting chitin is still a relatively new practice that has yet to cement effective, standard procedures. Cost of manufacturing this flexible film is also a consideration still being looked at.