Optimizing the Synergistic Effect: A Physical Blend of ZnO and CuO Nanoparticles Functionalized With Inula viscosa Extract as a Nanobioactive Coating for Superior Shelf-Life Extension of Chicken Meat

Abstract

This study developed and evaluated a novel, ternary active coating system based on sodium alginate functionalized with Inula viscosa extract-modified physical blend of zinc oxide (ZnO) and copper oxide (CuO) nanoparticles (IV-ZnO/CuO) for superior shelf-life extension of refrigerated chicken meat. Comprehensive characterization via X-ray diffraction (XRD) and atomic force microscopy (AFM) confirmed the successful synthesis of nanoscale, phase-pure structures with average crystallite sizes of 26 ± 2 nm (ZnO) and 21 ± 2 nm (CuO). The phytochemical-rich extract (185 ± 8 mg GAE/g) provided a strong antioxidant foundation (DPPH IC50: 12.5 µg/mL). Antimicrobial assessment revealed a clear synergistic effect, with the functionalized nanoparticles showing a 50%–55% reduction in minimum inhibitory concentration (MIC) against major foodborne pathogens compared to unmodified hybrids, supported by a fractional inhibitory concentration index (FICI) of ≤0.37. During 15-day storage at 4°C, the optimized coating (Alg-IV-NP) demonstrated exceptional preservation performance: it maintained microbial counts below the spoilage threshold (6 log CFU/g), achieving reductions of 3.2 and 2.9 log CFU/g for Staphylococcus aureus and Escherichia coli O157:H7, respectively. The coating effectively inhibited lipid oxidation, with thiobarbituric acid reactive substances (TBARS) values remaining at 0.35 ± 0.03 mg MDA/kg (vs. 0.92 ± 0.06 mg MDA/kg in controls) and well below the sensory rejection limit. It also preserved color stability (ΔE = 3.42 ± 0.31) and pH. A comprehensive safety assessment aligned with the safety-by-design paradigm showed excellent biocompatibility (>90% Caco-2 cell viability) and significantly reduced metal ion migration levels (Zn2+: 0.94 mg/kg; Cu2+: 1.12 mg/kg in 3% acetic acid), which were substantially below EU regulatory limits. This research presents an effective, green, and multifunctional strategy for active packaging, leveraging natural synergistic mechanisms to simultaneously combat microbial and oxidative spoilage, thereby offering a sustainable solution for enhancing the safety and shelf-life of highly perishable foods.