Effect of food simulants on stability of copper oxide in bionanocomposite food packaging film

Abstract

Addition of copper oxide nanoparticles (CuONPs) to poly (butylene‐adipate‐co‐terephthalate) (PBAT)/thermoplastic starch (TPS) biopolymer blend produced bionanocomposite films with improved mechanical and oxygen barrier properties, as well as enhanced other benefits including antimicrobial activity. In this study, the PBAT/TPS‐CuO bionanocomposite films with varying CuONPs contents (0.05%, 0.5%, 1%, and 2%) were challenged by food simulants (10% ethanol represented to aqueous food and 3% acetic acid represented to acidic food) in accordance with European Regulation 10/2011. CuONPs in the bionanocomposite films demonstrated good stability when exposed to 10% ethanol; however, it was dissolved in 3% acetic acid. The X‐ray diffraction and the energy dispersive spectroscopy results showed that CuONPs in the film were completely lost after acid exposure, whereas CuONPs in the films exposed to 10% EtOH were preserved. The maximum overall migration value was 5.0 mg/dm2. Inductively coupled plasma optical emission spectroscopy was used to confirm the presence of Cu in the simulants. The highest soluble Cu value of 12.39 mg/kg was detected from PBAT/TPS‐CuO2%, while migration value decreased as concentration ratio in film decreased. Although both values were within the threshold limits established by current legislation for non‐specific migration limit substances in food contact materials, the properties of bionanocomposite were altered. The mechanical properties of a post‐migrated PBAT‐TPS/CuO films taken from acidic conditions were reduced by 22% in tensile strength and 53% in elongation at break due to holes and microcracks on the film surface observed by scanning electron microscope. The average sealing strength of all bionanocomposite films decreased by about 25% after acid exposure. The oxygen permeability, on the other hand, was significantly improved, with a 16.3% reduction. Because the film had lost all of its active agent, film was unable to inhibit Escherichia coli growth. While 3% acetic acid caused dissolution of CuONPs and significant changes in properties of PBAT/TPS‐CuO film, 10% ethanol caused very minor to no changes in bionanocomposite film properties.