A research paper published on July 23, 2018, provides insight into new technology that uses crab shell (chitin nanofibers) and trees (cellulose nanocrystal) as barrier layers with polylactic acid (PLA) in packaging. The research was published in ACS Sustainable Chemistry & Engineering by a group from the School of Chemical and Biomolecular Engineering, Georgia Institute of Technology in Atlanta, led by J. Carson Meredith.
|Image courtesy ACS Sustainable
Chemistry & Engineering.
Chitin is an abundant biopolymer whose natural production is second only to cellulose. Similar to cellulose nanocrystals (CNCs) or nanofibers (CNFs), chitin nanofibers (ChNFs) can be isolated and used as sustainable O2 barrier materials in food, electronics and pharmaceutical packaging. These bioavailable nanomaterials are readily dispersed in water, enabling spray-coated films to be deposited at high rates onto uneven or delicate surfaces, according to an abstract of the research paper published on the ACS Sustainable Chemistry & Engineering website.
In the present study, the researchers demonstrated the successful layer-by-layer spray coating of cationic ChNF and anionic CNC suspensions onto PLA films. ChNF/CNC multilayers were found to lead to a reduction in the O2 permeability of the final composite film by as much as 73%, with the largest effects seen in composites with three alternating layers (ChNF-CNC-ChNF). Multilayer ChNF/CNC coatings were found to have lower O2 permeability and less haze than those coated with ChNF or CNC alone (72% and 86% less haze, respectively).
According to an article written by Natalie Parletta that appeared in Cosmos magazine, the researchers “had been investigating cellulose for its renewable plastic potential. They were exploring chitin for a different reason when it dawned on them that chitin’s nanofibers might complement the cellulose nanocrystals,” Parletta wrote.
“The chitin nanofibers are positively charged, and the cellulose nanocrystals are negatively charged,” Meredith explained. “They work well as alternating layers in coatings because they form a nice interface.”
After suspending the cellulose and chitin nanofibers in water, the team sprayed them onto a surface to create the material. It was discovered that, as an added benefit, the crystalline structure is more difficult for gas molecules to penetrate than plastic derived from PET.
“Our material showed up to a 67% reduction in oxygen permeability over some forms of PET, which means it could, in theory, keep foods fresher longer,” said Meredith.