Evaluation of a Gluten-Based Edible Film Incorporated with Beetroot Extract and ZnO Nanoparticles as an Active Food Packaging System

This study evaluated the application of a gluten-based edible film (GBEF) as a biodegradable active packaging (BAP) system made up of gluten incorporated with beetroot extract (BE) and ZnO nanoparticles (ZnONPs). The reliability of ratings of the compositions of GBEF was statistically analyzed using two-way analysis of variance with Tukey's post hoc test by assessing the functional properties as well as antioxidant and antibacterial activities. An increased amount of BE from 0.5 to 1.5% in the matrix of GBEF incorporated with 0.1% ZnONPs can increase the antioxidant activity (the 1,1-diphenyl-2-picrylhydrazyl assay) from 11.32 to 27.09%. In the matrix of GBEF incorporated with 0.5% BE, an increase in the amount of ZnONPs from 0.1 to 0.4% can enhance the antibacterial activity by 96.43% against Escherichia coli and by 40.00% against Staphylococcus aureus and decrease its antioxidant activity by 4.16% from 11.32 to 7.16%. The diameter sizes in the inhibition zones of E. coli and S. aureus differed from each other due to the electrostatic interactions of ZnONPs with E. coli being different from those with S. aureus. The combination of ZnONPs with BE created a tighter structure of the ZnO–gluten matrix with an even distribution of ZnONPs, which formed a barrier that caused a limited diffusion of water molecules. GBEF was characterized by a water vapor transmission rate below of 10 g/m2/24 h, thickness of less than 0.25 mm, tensile strength of stronger than 70 MPa, and elongation at break of greater than 0.3%, complying with Japanese Industrial Standards. The proposed BAP system will contribute to edible and eco-friendly food packaging applications.