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This study details the synthesis of tomato extract–magnetic iron oxide nanoparticles (TEx-MIONPs), focusing on the antioxidant capacity and food preservation applications. Utilizing key reagents, including 98% iron (III) chloride hexahydrate, a controlled process yielded TEx-MIONPs. The characterization involved X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR). XRD analysis revealed a predominant cubic magnetite structure. TEM and SEM depicted diverse morphologies, such as ultrasmall cubic and quasi-spherical structures. FTIR spectroscopy confirmed Fe–O bonds in a mixed phase of Fe₂O₈ and Fe₈O₄. Antioxidant activity assessment showcased the potent scavenging effects of TEx and TEx-MIONPs against DPPH free radicals, with 100% inhibition after 20 min and an IC50 of about 137 µg/mL, respectively. Furthermore, TEx-MIONPs, when stabilized with banana-based bioplastic and utilized as nanocoating preservation materials, demonstrated efficacy in grape preservation by exhibiting a lower weight loss rate compared to the control group over six days. Specifically, the weight loss rate for preserved grapes was 28.6% on day 6, contrasting with 34.6% for the control. This pioneering study amalgamates the natural antioxidant properties of tomatoes with the enhanced characteristics of magnetic iron oxide nanoparticles, offering sustainable solutions for food preservation and nanopackaging. Ongoing research aims to refine the experimental conditions and explore the broader applications of TEx-MIONPs in various contexts.

This study synthesizes magnetic iron oxide nanoparticles from agro-waste sweet pepper extract, exploring their potential as antioxidant additives and in food preservation. Iron (III) chloride hexahydrate is the precursor, with sweet pepper extract as both a reducing and capping agent at pH 7.5. Characterization techniques, including microscopy and spectroscopy, analyze the sweet pepper extract-magnetic iron oxide nanoparticles. Antioxidant capacities against 2,2-diphenyl-1-picrylhydrazyl are assessed, incorporating nanoparticles into banana-based bioplastic for grape preservation. Microscopy reveals cubic and quasi-spherical structures, and spectroscopy confirms functional groups, including Fe–O bonds. X-ray diffraction identifies cubic and monoclinic magnetite with a monoclinic hematite presence. Sweet pepper extract exhibits 100% inhibitory activity in 20 min, while sweet pepper extract-magnetic iron oxide nanoparticles show an IC50 of 128.1 µg/mL. Furthermore, these nanoparticles, stabilized with banana-based bioplastic, effectively preserve grapes, resulting in a 27.4% lower weight loss rate after 144 h compared to the control group (34.6%). This pioneering study encourages institutional research into the natural antioxidant properties of agrowaste sweet pepper combined with magnetic iron and other metal oxide nanoparticles, offering sustainable solutions for nanopackaging and food preservation. Current research focuses on refining experimental parameters and investigating diverse applications for sweet pepper extract-magnetic iron oxide nanoparticles in varied contexts.