Next-Generation Bioactive Coatings: Physicochemical, Antioxidant, and Antimicrobial Properties of ZnO-Enriched Plantago major L. Seed Mucilage Films

This study investigated the reinforcement of Plantago major L. seed mucilage-based films with zinc oxide (ZnO) nanoparticles and the effects of loading level on film performance. The ZnO-free control (PM) and films containing 0.5%, 1.0%, and 1.5% ZnO were compared in terms of physical, mechanical, thermal, structural, antioxidant, and antibacterial properties. At 1.5% ZnO, tensile strength increased from 28.70 ± 0.45 to 51.09 ± 0.12 MPa (a 78.0% increase), whereas elongation at break decreased from 24.72% ± 0.40% to 16.78% ± 0.29%. In the same group, moisture content decreased from 31.14% ± 0.10% to 24.32% ± 0.16%, and water-holding capacity declined from 3.51 ± 0.04 to 2.88 ± 0.03 g/g, while film thickness increased from 0.160 ± 0.002 to 0.292 ± 0.003 mm. DPPH radical-scavenging activity increased from 3.47% ± 0.07% to 39.70% ± 0.31%. At the highest ZnO level, the inhibition areas measured against Escherichia coli and Staphylococcus aureus were 20.54 ± 0.53 and 16.09 ± 0.33 mm2, respectively. DSC analysis showed decreasing reported transition temperatures and increasing endothermic transition enthalpy. SEM images revealed more pronounced surface heterogeneity at higher loading levels, whereas the characteristic bands of the polysaccharide film structure were retained in the FTIR spectra. These findings demonstrate that ZnO incorporation enhances the mechanical strength and measured bioactive responses of mucilage films, suggesting their potential as bioactive materials for food packaging applications. However, further studies are needed to evaluate their performance and safety under actual food packaging conditions.