Cellulose Nanofibril (CNF)-Coated PFAS-Free, Grease-Resistant All-Bio-Based Molded Pulp Containers for Food Packaging

Abstract

Food packaging is critical since proper packaging can extend the shelf life of foods. Currently, petroleum-based plastics, such as poly(ethylene terephthalate) (PET), polyethylene (PE), and polypropylene (PP), are commonly used as packaging materials, but they have led to a lot of waste and environmental pollution. In this study, a previously reported method was modified to fabricate a cellulose nanofiber (CNF) and carboxymethyl cellulose (CMC) paste to make it more homogeneous and less laborconsuming, and it was utilized it as a coating material for molded pulp (MP) food trays. A smooth and uniform dry CNF/CMC coating with a thickness of ∼200 μm was achieved via over-molding. To improve adhesion, chitosan was coated on the MP between layers. Uniaxial tension, "crush strength" compression, and "cross-hatch" and lap-shear adhesion tests were performed to characterize the mechanical enhancement by the coating. Gurley air porosity and water vapor transmission rate tests were conducted to compare the barrier properties against air and moisture between the CNF/CMC-coated MP trays and the uncoated MP trays. Oil and grease resistance testing using the TAPPI-T559 standard showed that coated samples can resist grease much better than uncoated samples. Finally, the trays were lidded with two different kinds of plastic films: poly(lactic acid) (PLA) and poly(ethylene terephthalate) (PET). Raspberries, blueberries, and cherry tomatoes were then used for food storage testing, where it was found that the coating helps extend the shelf life of fruits.

Sustainable biodegradable coatings for food packaging: challenges and opportunities

“…Chitosan provided electrostatic attraction with CNF/CMC, thereby improving the interlayer adhesion between CNF/CMC and MP. 214…”

“…Chitosan provided electrostatic attraction with CNF/CMC, thereby improving the interlayer adhesion between CNF/CMC and MP. 214 • Surface roughness: This is to create a rigid substrate, with peaks and valleys, to enhance the mechanical interlocking of the coating with the substrate. 212 For example, modification of acrylated epoxidized linseed oil with beeswax provided a stable wax-oil emulsion coating for paper packaging.…”