Exploring the antimicrobial efficacy and preservation potential of alginate-based edible films enriched with cinnamon and lemongrass essential oils on minimally processed carrots
K.G. Kaushani, Gayan Priyadarshana, Nuwanthi P. Katuwavila, Randika Jayasinghe, A.H.L.R. Nilmini
Abstract
• Alginate films with different concentrations of cinnamon (CEO) and lemongrass essential oil (LEO) are optimized. • CEO and LEO at 1% and 1.5% show effective antimicrobial and antioxidant properties. • The water resistance and mechanical properties were enhanced with essential oils. • Films exhibit improved thermal stability and unique morphologies. • Novel alginate films enhance food quality, promoting preservation and sustainability. There is a growing demand for sustainable packaging developed using novel biodegradable materials instead of synthetic packaging. This study aimed to develop edible biodegradable active food packaging films to extend the shelf life of minimally processed foods. Alginate-based active edible films incorporating cinnamon essential oil and lemongrass essential oil at various concentrations (0.5%, 1%, and 1.5%) were developed and characterized for their physical, optical, mechanical, antioxidant, and antimicrobial properties, as well as soil biodegradability. The films were analyzed using thermogravimetric analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The tensile strength of the composite films decreased from 2.08 to 1.81 MPa with the incorporation of essential oils, while the percentage elongation at break improved from 67.73 to 74.15%. Adding essential oils enhanced water resistance, decreased the water vapor transition rate, and increased water contact angles by 24–46% and 29–50% for cinnamon and lemongrass essential oil incorporated films, respectively. Antimicrobial activity was significant against Staphylococcus aureus, Bacillus cereus, Klebsiella pneumoniae , and Escherichia coli , with 1% cinnamon essential oil and 1.5% lemongrass essential oil showing the highest inhibition. Films containing 1.5% essential oil concentrations showed the highest DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging assay with IC 50 values of 0.15 and 0.19 mg/mL for cinnamon and lemongrass essential oil, respectively), confirming their strong antioxidant properties. In Fourier transform infrared spectroscopy analysis, distinctive peaks associated with the components of the film were identified and reported at their respective positions. The incorporation of essential oils improved the thermal stability of the films. Scanning electron microscopy analysis indicated varying film morphologies based on composition, highlighting increased heterogeneity with essential oil incorporation. The application of active edible films on minimally processed carrots revealed that alginate-based films, when incorporated with cinnamon and lemongrass essential oil, effectively preserved minimally processed carrots. This preservation was evident through reduced weight loss, changes in moisture content, pH, titratable acidity, whiteness index changes, and microbial counts (total mesophiles, yeast, and molds) during cold storage. Overall, these films offer a sustainable solution to address the perishability challenges associated with minimally processed foods.