Preparation, characterization and antioxidant properties of gelatin films incorporated with Origanum onites L. essential oil

This study aims to develop gelatin (GEL) films containing 0, 2, 4, 6, and 8% Origanum onites L. essential oil (OOEO) with glycerol as plasticizer using the casting technique. The physical, color, mechanical, structural, thermal, and antioxidant properties of enriched GEL films were also characterized. The GEL/OOEO combination significantly reduced tensile strength and film solubility of GEL-based films while significantly increasing ultraviolet and visible light barrier properties, thickness, and elongation at break (p ≤ 0.05). According to the results, the increased OOEO content has become darker yellow compared to the control GEL film. The amount of compounds in OOEO was determined using gas chromatography coupled with mass spectrometry, and it was determined that the most representative compounds of OOEO were carvacrol and thymol. As OOEO concentration increases, the decrease in the smooth, continuous surfaces and dense internal structures of GEL/OOEO films are observed with scanning electron microscopy. FTIR analysis showed some changes in the density of typical bands of control GEL and GEL/OOEO films. Analysis of thermal properties was determined by DSC, and films containing OOEO showed two different endothermic peaks at a lower temperature than control films. The antioxidant properties were significantly enhanced with increasing OOEO concentration reaching 21.78 and 46.52% of DPPH and 52.16 and 83.13% of ABTS radical inhibition, respectively. Therefore, GEL/OOEO films may be suitable for use as an environmentally friendly active film due to their excellent antioxidant properties with sufficient functional properties, depending on the desired application.