The use of plastic films to protect food from spoilage has revolutionized the global food production system. As previously reported on this blog, the environmental impact of throwing food away when it has gone bad is often much greater than the impact of the plastics used to package the food. For example, one company reports findings that only 11% of the CO2 emitted during the food production and transport process is associated with plastic packaging; in contrast, 89% of the CO2 is associated with the rest of the food production process, including growing, refrigerating, and transporting the food. If food is thrown away because it isn’t sufficiently protected by packaging, that 89% has gone to waste.
Given the importance of food packaging to the global food production system, it’s no surprise that researchers are looking for more sustainable ways to create food packaging films.
Last month, a team of researchers published a paper in ACS Sustainable Chemistry and Engineering titled “Spray-Coated Multilayer Cellulose Nanocrystal—Chitin Nanofiber Films for Barrier Applications”. Although the title is a bit of a mouthful, the new polymer film presented in the paper is made from two simple, naturally occurring ingredients: cellulose and chitin. Cellulose, which has been described as the most abundant biopolymer on the planet, is found in all woody plant materials and is readily available as an agricultural bi-product. Chitin, the other feedstock, is also produced in nature. Although it is most commonly found in the shells of marine animals such as crabs, it is also present in some species of fungus.
The research team found that they could create an impermeable plastic film by suspending forms of both polymers in water and spraying the water onto a flat surface in a thin layer.
The resulting material is a thin, transparent sheet that is strong and malleable like a traditional plastic film. The material exhibits a low oxygen permeability (a 67% reduction compared to some existing plastic films). This means it should be effective in preventing food spoilage.
Despite its promise, the material does need some work before it’s ready for scaled-up production. One issue is that the material is not completely impermeable to water vapour, meaning it could allow moisture from outside to enter dry food and could allow moisture to escape in dry environments, speeding spoilage of foods with higher moisture content. Another issue is that people with shellfish allergies could potentially have a reaction to the plastics (this is unlikely due to the high degree of chitin purity, but it nevertheless creates a need for more stringent testing.
For another take on the story, check out this article, published in Physics World.