Preparation and characterization of corn starch-based food packaging films: effects of thymol essential oil and ZnO nanoparticles on physicochemical, mechanical, barrier, thermal, and antimicrobial properties

Abstract

Conventional petroleum-based food packaging materials pose significant environmental challenges due to their non-biodegradable nature, highlighting the need for sustainable alternatives with enhanced functional properties. Therefore, this study aimed to develop biodegradable corn starch-based composite films incorporated with varying concentrations of thymol essential oil (0.1, 0.2, and 0.3 wt% of corn starch) and ZnO nanoparticles (5, 16, 28, and 33 wt% of corn starch) and to evaluate their physicochemical, structural, thermal, and antimicrobial properties. The films were characterized using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and other physicochemical analyses, while their antimicrobial activity against Staphylococcus aureus was also investigated. The results demonstrated that ZnO nanoparticles significantly enhanced the thermal stability and crystallinity of the corn starch films, whereas thymol essential oil markedly improved their antimicrobial activity. Among all formulations, the film containing 0.3 wt% thymol and 28 wt% ZnO nanoparticles exhibited the well-balanced performance, showing improved mechanical strength, reduced water vapor permeability, enhanced structural integrity, and effective antimicrobial activity. The incorporation of thymol and ZnO nanoparticles also influenced the films’ thickness and optical properties, indicating successful modification of the starch matrix. These findings demonstrate that thymol- and ZnO nanoparticle-reinforced corn starch films are promising biodegradable materials for active food packaging applications by combining improved barrier, mechanical, thermal, and antimicrobial properties.