Optimisation of pulsed electric fields processing parameters for developing biodegradable films using zein, chitosan and poly(vinyl alcohol)

This study investigated the feasibility of using pulsed electric fields (PEF) to develop biodegradable films from biopolymers (zein, chitosan) and biosynthetic polymers (poly(vinyl alcohol), polyethylene glycol). Various responses including the viscosity, loss modulus, particle size and polydispersity index of the dispersions were determined after PEF processing at various electric field strengths (0.9-3.5 kV/cm), pulse frequencies (50-300 Hz), and specific energies (80-650 kJ/kg). The structure-function relationship between the PEF processed colloidal dispersions, and the effect of PEF on the resulting films was evaluated using the tensile strength, Young's modulus, and erosion index. The viscosity and loss modulus decreased, but the particle size increased at a field strength above 2.4 kV/cm and specific energy below 200 kJ/kg. The films showed higher tensile strength and Young's modulus but low erodibility at a field strength/frequency/specific energy of 2.4 kV/cm/< 100 Hz/ < 100 kJ/kg, respectively. The optimum tensile strength (maximised) (32.89 MPa) and erosion index (minimised) (33.42%) were obtainable at a field strength/frequency/specific energy of 3.4 kV/cm/50 Hz/100 kJ/kg, respectively. The results of scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry depicted improvements in the compatibility and nature of intra-/intermolecular interactions between biomacromolecules, as evidenced by the modifications in the morphology, crystallinity and thermal properties. These findings demonstrate the potential of using PEF as a pre-treatment technique during the production of biodegradable films from colloidal dispersions. Industrial relevance. The combinations of PEF processing parameters investigated in this study can be employed to elicit microstructural modifications of colloidal dispersions. PEF-induced effects on colloidal systems can be translated into a functional modification of assembled biological materials (e.g. biodegradable films). The study illustrates possible designs for a PEF process for utilisation of agro-based co-products to meet the demand for eco-friendly materials.