Gelatin-based edible coatings enriched with summer savory essential oil: a natural strategy to enhance stability of rainbow trout

This study investigated the effects of gelatin-based edible coatings enriched with summer savory (Satureja hortensis) essential oil (0.5–2%) on the quality of rainbow trout (Oncorhynchus mykiss) fillets during 12 days of refrigerated storage. FTIR and SEM analyses confirmed the successful incorporation of essential oil into the gelatin matrix and revealed structural modifications in the coating films. Microbiological evaluation showed that coated fillets, particularly those with higher oil concentrations, exhibited significantly lower counts of mesophilic and psychrotrophic bacteria, as well as yeast and mold, compared with the control group. Chemical indicators, including total volatile basic nitrogen and thiobarbituric acid reactive substances, were markedly reduced in treated samples, indicating delayed protein degradation and lipid oxidation. pH values remained more stable in coated fillets throughout storage. Sensory evaluation and color measurements further demonstrated that the coatings preserved desirable quality attributes and improved quality during refrigerated storage. Overall, these findings suggest that gelatin-based coatings enriched with summer savory essential oil represent a promising natural preservation strategy for improving the microbiological, oxidative, and sensory quality of refrigerated rainbow trout fillets.