Gelatin-Chitosan Based Composite Films Enriched with Satureja kermanshahensis Jamzad Essential Oil Nanoemulsion and Carbon Dots: Characterization and Functional Properties

Gelatin-chitosan-based (GL-CS) functional films were synthesized by incorporating a nanoemulsion (NE) containing the essential oil (EO) of Satureja kermanshahensis Jamzad, commonly referred to as "Marzeh Kermanshahi" (MK) in Persian. These films also incorporated different concentrations (1%, 2%, and 3%) of carbon dots (CDs) derived from citric acid and urea. The physical, mechanical, optical, structural, and barrier characteristics, alongside the assessment of antioxidant and antibacterial efficacy of the resultant films, were thoroughly characterized and examined. The sizes of MK-EONE and CDs, as measured by a Zetasizer, were determined to be 118 nm and 1.2 nm, respectively. Fourier-Transform Infrared (FTIR) spectra and Scanning Electron Microscopy (SEM) of the films indicated favorable compatibility between both polymers, MK-EONE, and 1% CD, with uniform dispersion within the polymer matrix. The composite film containing MK-EONE and 1% CD exhibited enhanced UV protection, mechanical properties, and glass transition temperature (Tg). However, certain characteristics, such as water solubility, water vapor permeability (WVP), hydrophobicity, and transparency, demonstrated a decrease. Furthermore, the films incorporating MK-EONE and CDs demonstrated strong antioxidant activity, assessed through the DPPH method, and potent antimicrobial effectiveness against foodborne pathogens like Staphylococcus aureus, Bacillus cereus, and Escherichia coli. Consequently, the GL-CS-MK-EONE-CDs film, characterized by its superior functional attributes, shows promise for applications in food packaging.