Enhanced Bread Shelf Life Using Carboxymethyl Cellulose Composite Films with Combined Antibacterial Activity of Zinc Oxide and Cinnamon Essential Oil

Abstract

Cellulose is the most abundant natural polymer and is widely used in the packaging industry. One of the primary functions of food packaging is to protect food products from spoilage and extend their shelf life. Although cellulose lacks inherent antimicrobial activity, this limitation can be addressed through appropriate chemical or physical modifications to impart antimicrobial properties to cellulose-based materials. Nevertheless, cellulose represents a suitable matrix for the incorporation of various antimicrobial agents, enabling the development of active packaging materials. Moreover, the combination of multiple antimicrobial agents may result in combined effects, potentially providing broader and enhanced antimicrobial activity while reducing the overall amount of antimicrobial agents required. Herein, we report the preparation of a highly potent antimicrobial composite based on carboxymethyl cellulose (CMC) and zinc oxide (ZnO) nanoparticles (NPs) loaded with cinnamon essential oil (CEO). The composites were characterized using FTIR, UV–Vis, and fluorescence spectroscopy, scanning electron microscopy (SEM), and thermal analysis. Their mechanical and antibacterial properties, as well as potential biodegradability, were evaluated. The resulting films exhibited good barrier properties and enhanced mechanical performance. Although the composite films are composed of a food additive, spice extract, and ZnO NPs, all of which are generally recognized as safe (GRAS), the resulting innovative packaging exhibited strong antibacterial activity against E. coli and S. aureus, with inhibition zones reaching up to 38 mm. Moreover, no viable colonies of planktonic bacterial cells were detected after 4 h of incubation. In preliminary tests, no visible mold growth was observed on bread slices packaged in these films after 28 days of storage, whereas the control samples showed visible spoilage as early as day 7.