Investigation of the effects of nanoemulsions created with sunflower oil combination of extracts obtained from olive leaves by different extraction methods on seabas (dicentrarchus labrax).

Phenolic extracts obtained from olive leaves through different extraction methods (classical solvent extraction, Soxhlet, and ultrasonic extraction) were utilized in the formulation of nanoemulsions with sunflower oil, and the effects of these formulations on the quality and shelf life of sea bass (Dicentrarchus labrax) fillets were investigated. Within the scope of the study, olive leaf extracts were obtained using ethanol and hexane as solvents through classical solvent extraction, Soxhlet, and ultrasonic extraction techniques. Comparative analyses revealed that ultrasonic extraction provided the highest yield in terms of total phenolic content and antioxidant capacity. Therefore, nanoemulsions were prepared with extracts obtained by the ultrasonic method at concentrations of 0.1%, 0.3%, and 0.5%. The extracts were formulated into nanoemulsions with sunflower oil, surfactants, and varying concentrations of extracts, and their physical (droplet size, zeta potential, polydispersity index) and chemical (antioxidant capacity) properties were analyzed. Fillets in the control group and those treated with 0.1% extract-containing nanoemulsions were found to be acceptable for consumption up to day 5 under cold storage (4 °C), while samples treated with nanoemulsions containing 0.3% and 0.5% extract extended the shelf life to day 7. Thus, high-extract-concentration nanoemulsions provided approximately a two-day improvement in shelf life compared to the control group. Similarly, oxidation indicators (peroxide value, TBA) and total volatile basic nitrogen (TVB-N) analyses demonstrated lower values in the nanoemulsion-treated groups, indicating a delayed spoilage process in fish fillets. In conclusion, the application of nanoemulsions prepared with extracts obtained by ultrasonic extraction was shown to provide the most effective combination, resulting in an extension of shelf life by about two days in sea bass fillets. These findings highlight that olive leaf-derived natural phenolics represent an effective approach for both preserving seafood quality and extending storage stability. Key Words: Olive leaf, oleuropein, extraction, sea bass, nanoemulsions