Improving properties of canola protein-based biodegradable films using chitosan for food packaging applications

Abstract: One major challenge the food industry faces is the overuse of non-decomposable plastic in its packaging sector, which causes environmental and health issues. A more sustainable approach to this matter is to use biopolymers such as proteins and polysaccharides to produce packaging films, whose materials are universally known to be renewable, safe and biodegradable. However, packaging material made from a single biopolymer often lacks strength, moisture, and gas barrier properties; therefore, composite packaging films made from polymer blends such as protein-polysaccharides have gained more interest. This work investigates the potential incorporation of chitosan at different levels (0%, 1%, 3%, 5% and 7% w/v) into canola protein-based films to improve the film’s functional properties. Canola protein is an underutilized biopolymer that has been slowly gaining recognition due to its low cost and good properties for film fabrication, while chitosan can improve the film’s mechanical and gas barrier properties. The films were fabricated using a modified solvent casting method. The mechanical properties, water solubilities, water vapour permeability and contact angle of the protein-chitosan films were determined. In mechanical properties analysis, tensile strength (MPa), elongation at break (%) and Young’s modulus (MPa) of the control films were 6.67 MPa (±0.5 MPa), 28.49% (± 5.2%) and 187.25 MPa (±72.1 MPa) respectively. When different concentrations of chitosan were added, there was an increase in all response variables until 3%, followed by a decline. A similar trend was observed regarding hydrophobicity, where the contact angle of the controlled films (84o ±2.7o) increased up to 5% chitosan (92o ±1.03o) and gradually decreased. A significant difference (p <0.05) was detected in the tensile strength of 3% chitosan films and the contact angle of 3% and 5% chitosan films compared to those of controlled films. Since canola protein and chitosan are hydrophilic, no significant difference was observed in the films' water vapour permeability and solubility. The results suggest that 3% chitosan can potentially improve the mechanical properties of the canola protein films.