Cellulose Nanomaterials in Sustainable Food Packaging: Enhancing Barrier Performance from Coatings to Multilayer Films

Abstract

Food packaging plays a crucial part, yet the use of petroleum-based plastics has led to environmental concerns. Researchers have been exploring sustainable alternatives using CNMs. This dissertation includes three parts, each focusing on using CNF or CNC for packaging applications. In the first project, CNF/CMC coated MP trays were achieved via over-molding. Mechanical, Gurley air porosity and water vapor transmission rate testing showed that the coating improved the overall performance. Coated samples showed the highest oil and grease resistance level. Fresh fruit testing showed that the coating helps elongate the shelf life of fruits. In the second project study, to overcome the problem of relatively poor water barrier performance of CNF/CMC coatings in high humidity conditions, coatings were chemically modified by crosslinking with PAE and incorporated with Cloisite-Na⁺ nano-clay and PVA. The chemical modification enhanced both water and oxygen barrier performance and reduced Cobb value. The formulated CNF-coated MP trays maintained the same level of oil and grease resistance. Mechanical testing showed reduced Young’s modulus, similar UTS, and higher strain at break for formulated CNF-coated tray samples compared to the un-crosslinked samples. In the third project, a transparent tri-layer PLA-CNC/PVA-PLA film was successfully fabricated using blade coating and lamination. The CNC/PVA coating (~ 6μm) showed a high degree of CNC alignment and significantly enhanced the gas barrier properties. Furthermore, these laminates were formed into bags where a fruit storage test showed that the PLA-CNC/PVA-PLA could elongate the shelf life of fresh apple slices based on weight loss and enzymatic browning.