Effects of Different Types of Pectin on the Properties and Structure of Gelatin Essential Oil Edible Films

In this study, the essential oils cinnamaldehyde, eugenol, and anisaldehyde were complexed to investigate their bacteriostatic properties against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Pseudomonas oryzae. Utilizing gelatin as the primary film-forming matrix and the blended essential oils as bacteriostatic agents, the effects of incorporating various types of dextran into gelatin-based edible films were examined. The objective was to provide data to support the use of dextran in edible films, aiming to develop films with enhanced performance. Performance characterization studies of four composite edible films were conducted using infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The results indicated that the optimal combination of essential oils was a 1:1 ratio of cinnamaldehyde to eugenol, yielding the lowest inhibitory concentration of 0.156 μL/mL for both Escherichia coli and Pseudomonas aeruginosa, and 0.313 μL/mL for Bacillus subtilis and Pseudomonas oryzae. Additionally, the incorporation of dextran significantly enhanced the mechanical properties, barrier properties, and thermal stability of both gelatin-based edible films and those infused with essential oils. Specifically, the mechanical properties improved as follows: tensile strength at break (TS) increased from 35%~40% to 45%~55%, elongation (E) rose from 15~17 MPa to 20~23 MPa, water vapor permeability (WVP) decreased from 30.04×10−2 g·mm/(m²·h·kPa) to 22.31×10−2 g·mm/(m²·h·kPa). Oil permeability (PO) was reduced from 139.12 g·mm·m−2·d−1 to 108.21 g·mm·m−2·d−1, and oxygen permeability (PV) decreased from 5.72 g/100 g to 3.46 g/100 g. Infrared spectroscopy, X-ray diffraction, and thermal stability analyses revealed strong interactions and improved compatibility between the dextran, essential oils, and gelatin. Furthermore, the film solution containing compound essential oil at the lowest inhibitory concentration demonstrated a significant antibacterial effect against the test bacteria, and the inhibition circle changed from 0~5 mm to 15~20 mm, reaching a medium sensitivity.