Desenvolvimento e caracterização de nanocompósitos de Kefiran/Carboximetilcelulose/ZnO Nps para aplicações em embalagens de alimentos

Abstract

Polysaccharides are polymers derived from natural and renewable sources, which can be utilized in various applications, including the packaging industry. Kefiran is one of these polymers that has gained prominence recently due to its antimicrobial properties. Several studies have sought to combine the intrinsic properties of kefiran with other biopolymers and oxide nanoparticles as an effective alternative for producing active food packaging. In this context, the present study investigates, in detail, the development of films and edible coatings based on kefiran, carboxymethyl cellulose (CMC), and zinc oxide nanoparticles (ZnO NPs) for food packaging applications. Kefiran was extracted and purified from kefir grains, and its purity and structural features were confirmed by proton and carbon nuclear magnetic resonance (¹H and ¹³C NMR), Fourier-transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC). For the first time, kefiran exhibited significant antibiofilm activity against Staphylococcus epidermidis ATCC 35984, achieving eradication at 512 mg/L (p < 0.001). At the same time, ZnO NPs were synthesized via a microwave-assisted hydrothermal method and showed high crystallinity and distinct morphologies. These nanoparticles exhibited selective bactericidal activity against Gram-positive multidrug-resistant bacteria, primarily due to the generation of reactive oxygen species (ROS), especially hydroxyl radicals. Statistical analyses demonstrated that minimum inhibitory concentrations (MICs) of 256 and 512 mg/mL were effective in bacterial inhibition, highlighting the potential of ZnO NPs for functionalization in bio-based packaging systems. Subsequently, nanocomposite films were prepared by incorporating ZnO NPs into the kefiran/CMC matrix at different concentrations (5, 10, and 25% w/w), and their physicochemical, mechanical, structural, and functional properties were thoroughly evaluated. Characterization techniques, including Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy, Fourier-Transform Infrared Spectroscopy (FT-IR), and Ultraviolet–Visible (UV-Vis) spectroscopy, revealed significant morphological, structural, and optical changes resulting from the incorporation of ZnO NPs. The nanocomposites exhibited improved mechanical strength, UV-blocking capacity, and water vapor barrier properties. Additionally, the films demonstrated enhanced antimicrobial activity, particularly against Staphylococcus aureus, indicating their suitability for active food packaging applications.