Konjac glucomannan/pectin composite films enriched with essential oil for chili preservation

The development of biodegradable active packaging materials has attracted increasing attention as a sustainable alternative to petroleum-based plastics for extending the shelf life of fresh produce. This study developed konjac glucomannan (KGM)/pectin composite films containing Zanthoxylum limonella essential oil (ZO) and systematically evaluated their physicochemical, antimicrobial, and preservation properties for fresh chili peppers. Films containing 0, 2.5, and 5.0% ZO were prepared by solvent casting and characterized using tensile testing, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), contact angle measurement, thermogravimetric analysis (TGA), water vapor permeability (WVP), antibacterial assays, and storage tests. Incorporation of ZO significantly affected film properties in a concentration-dependent manner. Compared with the control film, the 2.5% ZO formulation exhibited the most balanced performance, with tensile strength decreasing from 58.68 ± 1.72 to 41.19 ± 2.23 MPa, elongation at break increasing from 21.84 ± 6.38 to 59.76 ± 21.66%, and the water contact angle increasing from 70.75 ± 1.21° to 95.37 ± 3.23°, indicating enhanced flexibility and surface hydrophobicity. FTIR and SEM analyses indicated changes in intermolecular interactions and film microstructure following ZO incorporation, whereas excessive ZO loading (5%) induced phase separation and reduced mechanical performance. The 5% ZO film exhibited the strongest antibacterial activity, producing inhibition zones of 17.35 ± 1.02 mm against Escherichia coli and 17.91 ± 1.82 mm against Staphylococcus aureus. Application to fresh chili peppers demonstrated that ZO-containing films reduced weight loss, maintained firmness, and delayed visible deterioration throughout the 14-day storage period compared with uncoated and neat-film controls. These findings demonstrate that KGM/pectin–ZO composite films are promising biodegradable active packaging materials, with the 2.5% ZO formulation providing the optimal balance between film performance and preservation efficacy for fresh chili preservation.