Preparation and characterization of bionanocomposites based on protein and cellulose nanocrystals by continuous casting

Abstract

This Ph.D. thesis covers the production and characterization of gelatin-cellulose nanocrystals (CNCs) bionanocomposite films intended for multifunctional food packaging. The up-scalability of the gelatin/CNCs films was attained by continuous casting and the rheological parameters of the film-forming solutions and drying temperature required to produce 12 m film/h were established. The continuous casting processing was proven to be advantageous when compared to the bench solution casting method. Tensile test, thermogravimetric analysis, and water vapor permeability analysis showed that the continuously cast gelatin/CNCs films had exceptionally better performance than the films obtained by bench casting. The physical and structural properties of the gelatin/CNCs bionanocomposites as tailored by pH-dependent electrostatic interactions were investigated. The suitability of CNCs was successfully extended by functionalization with rosin (r-CNCs), thus giving rise to antimicrobial reinforcing agents. Tensile test and antimicrobial analysis showed that r-CNCs served as bacterial nanofillers in gelatin-based films, which otherwise would suffer from limited physical and biological properties. Plant-derived tannic acid was successfully used as an antioxidant and bactericidal additive, as another perspective of extending the potential of the gelatin/CNCs films as a packaging material. Non-oxidized tannic acid favored non-covalent interactions and intermolecular connections between gelatin, CNCs, and tannic acid. These physico chemical interactions showed to have a greater influence on the antioxidant and physical properties of gelatin/CNCs/Tannic acid films. This thesis provides a comprehensive understanding of how CNCs can be explored to develop biodegradable films based on gelatin with enhanced properties or extra functionalities. A continuous solution casting was applied for scaling up the production of gelatin/CNCs-based films making them highly desirable for packaging applications.