Enhancing the functional properties of canola protein-based films using essential oils and polyvinyl alcohol

Abstract

The growing demand for sustainable food packaging has intensified interest in biodegradable polymer films with enhanced functional and mechanical performance. Canola protein is a promising plant-based biopolymer; however, its application is limited by poor mechanical strength, water sensitivity, and limited antimicrobial activity. This thesis aimed to address these challenges by incorporating essential oils with antimicrobial properties into canola protein films and blending canola protein with polyvinyl alcohol (PVA) to improve film strength and stability. All films were fabricated using the solvent-casting method. Their mechanical properties, moisture-barrier performance, and thermal characteristics were evaluated. In the first study, two essential oils carvacrol and cinnamaldehyde were incorporated into canola protein-based films at various oil concentrations (0%, 1%, 3% and 5%, v/v) and proportions (0:1, 1:0, 1:1, 1:2, 2:1, 1:4 and 4:1). The objective of the first study was to explore the potential to develop an active canola protein-based films infused with carvacrol and cinnamaldehyde and to evaluate their influence on the films’ properties. The addition of essential oils successfully imparted antimicrobial activity against Escherichia coli and Staphylococcus aureus. The 3% oil concentration was found to be optimal, achieving good antimicrobial activity while having minimal negative effects on other film properties. In the second study, canola protein-PVA composite films were prepared at blend ratios of 100:0, 90:10, 80:20, 70:30, 60:40, and 0:100. The objective of the second study is to investigate the effect of PVA incorporation on the functional properties of the canola protein-based films. The addition of PVA enhanced both tensile strength and flexibility, with the 60:40 canola:PVA film showing the best performance, exhibiting approximately a 155% increase in tensile strength (TS) and a 106% increase in elongation at break (EB) compared to pure canola protein films (TS 1.73 ± 0.33 MPa, EB 57.53 ± 8.57 %). Although water vapor permeability was not significantly affected, a decreasing trend was observed with increasing PVA content. Collectively, the findings from both studies demonstrate that essential oil incorporation and PVA blending are effective strategies for enhancing the functionality of canola protein-based films. These results support the development of biodegradable packaging materials with improved antimicrobial properties and mechanical stability, contributing to more sustainable alternatives for food packaging applications.