Physico-mechanical, Antimicrobial, and Antioxidant Properties of Gelatin Edible Films Incorporated with Olibanum Essential Oil and Sodium Hexametaphosphate on the Rainbow Trout Fillet Under Refrigerated Conditions

The present study was conducted to investigate the effect of sodium hexametaphosphate (SHMP) (0, 0.1, 0.2, and 0.3 g), and olibanum essential oil (OEO; 0, 2%, 4%, and 6% w/v) on the physicochemical, structural, antioxidant, and microbial properties of the gelatin-based edible film, and its effect on the refrigerated storage period of rainbow trout fillet. The results demonstrated that the water solubility, the water vapor permeability, mechanical properties, and antioxidant activity of all treatments were significantly improved compared to the control treatment. The Fourier-transform infrared spectroscopy analysis revealed 1035–1015 cm⁻¹ stretching vibrations of the C–C, and C–O groups, confirming ester linkages among the gelatin (G), SHMP, and OEO components. The treatments containing SHMP, and OEO exhibited acceptable antimicrobial activity against the tested Gram-positive, and Gram-negative microorganisms (Staphylococcus aureus, Escherichia coli, and Bacillus cereus). Moreover, the total count (TC), and Enterobacteriaceae count (EC) of rainbow trout fillets were significantly reduced by the optimal treatments of edible films (0.3 SHMP, 4% OEO- 0.2 SHMP, and 4% OEO) during 21-day refrigerated storage. According to the findings of this study, G/SHMP/OEO films could be a promising tool for packaging and protecting meat-based foods.