Spray coating of edible insect waxes for liquid food packaging

Abstract

In this study, insect waxes (Beeswax and Shellac wax) were spray-coated onto paper, cups, and bowls to achieve surface hydrophobicity for packaging applications. The thin coatings of wax mixtures with different ratios of waxes were employed at various annealing temperatures and studied in detail for the thermal, chemical, surface, and barrier properties of 20 coated papers. SEM confirmed the presence of multi-structured wax particles on the surface of coated papers only when annealed up to 80 °C (at 100 °C complete melting of wax particles occurred), where increasing Shellac wax in the wax mixtures resulted in large aggregates of wax particles on the paper. FTIR confirmed Beeswax with shorter fatty acid chains, comparing Shellac wax with longer fatty acid chains. Additionally, DSC confirmed a lower melting point for Beeswax, comparing Shellac wax with the higher melting point. The robustness of waxes after annealing was evident from the tape and crinkle tests. The spray-coated paper with insect wax mixture showed good repellency towards different food simulants, such as water, acetic acid, ethanol, octane, and several food products, as measured using contact angles. Lowered water absorption was noted for coated pulp-based bowls. The coating also showed self-cleaning or anti-fouling properties.