Strong and Transparent Deacetylated Chitin Nanofibril Films using Bees’ Honey and Carrageenan as Potential Plasticizers in Packaging

Honey from bees and carrageenan from red seaweeds may act as alternative plasticizers to commercial glycerol in improving the mechanical flexibility of deacetylated chitin nanofibril (DeChNF) films. Free-standing films with plasticizer content up to 65% were produced using a casting technique. Transparency, thermal relaxation, tensile properties, water absorption capacity, and water vapor permeability of the films were evaluated as essential properties in packaging. Firstly, the deacetylated ChNF film had a transmittance of 84.9% at 800 nm, with films containing 20 wt% plasticizers displaying transmittance values of 87.8% (glycerol), 83.6% (honey), and 85.4% (carrageenan). Secondly, Differential Scanning Calorimetry (DSC) indicated relaxation temperatures between 40–80ºC and 300–370ºC towards lower values with the plasticizer content. A more profound plasticization effect appears to be associated with honey, followed by glycerol, and finally, carrageenan. Thirdly, mechanical testing revealed a decrease in tensile strength from 41.3 MPa for pure DeChNF to 6.3 MPa (glycerol), 4.3 MPa (honey), and 9.4 MPa (carrageenan). Tensile strain increased from 8.5% for DeChNF to 24.74% (glycerol), 31.5% (honey), and 21.65% (carrageenan). Fourthly, water absorption capacity and water vapor permeability performance are compared to commercial packaging films. Thus, the data from DeChNF plasticized films with honey and carrageenan are novel and promising for innovative chitin nanofibril applications in packaging.