Multifunctional polylactic acid-tragacanth gum films containing shirazi thyme essential oil (Zataria multiflora Boiss): A structural and functional evaluation for active packaging

• Shirazi thyme essential oil (TEO) was successfully incorporated into PLA/KG biodegradable films. • TEO significantly improved the films’ antimicrobial and antioxidant activity in a dose-dependent manner. • Physicomechanical properties, including tensile strength and flexibility, were enhanced by TEO addition. • FTIR, XRD, and SEM analyses confirmed structural interactions and morphological changes in the films. • PLA/KG/TEO films show strong potential as sustainable active packaging materials for food preservation. This study aimed to develop a biodegradable film based on polylactic acid (PLA) and tragacanth gum (Katira gum, KG), enriched with Shirazi thyme essential oil (TEO), for sustainable active food packaging.TEO was extracted and chemically profiled using GC–MS, identifying carvacrol (71.12%) as the major constituent. The films were fabricated by incorporating different concentrations of TEO (0.3%, 0.6%, and 0.9%) into the PLA/KG matrix and evaluated for their structural, physicomechanical, and functional properties. The incorporation of TEO led to a concentration-dependent reduction in moisture content and solubility, a moderate increase in film thickness and opacity, and altered water vapor permeability (WVP), with the lowest WVP observed at 0.3% TEO. Mechanical testing revealed that TEO significantly enhanced the tensile strength and flexibility of the films. FTIR and XRD analyses confirmed intermolecular interactions and improved crystallinity without disrupting the polymer structure, while SEM images showed increased surface roughness and porosity at higher TEO levels. Functionally, the films exhibited strong antifungal and antibacterial activity against major foodborne pathogens, particularly Gram-positive bacteria, and demonstrated enhanced antioxidant potential, attributed to the high carvacrol content of TEO. These findings suggest that PLA/KG/TEO composite films hold promise as multifunctional, eco-friendly packaging materials with potential to improve food preservation and safety.