Edible coating enriched with rosemary extracts to enhance oxidative and microbial stability of smoked eel fillets

The antioxidant and antimicrobial properties of rosemary essential oil (EO) and extracts, entrapped in carboxyl methyl cellulose (CMC) edible coating for smoked eel were investigated. Analysis of the EO indicated 1,8-cineole, L-camphor, a-pinene, and 1-borneol, as the main components. The solid residue generated by the EO distillation was extracted in an ultrasound bath with ethanol to give an extract rich in rosmarinic acid, diterpenes and flavonoids. The addition of the extract at 200-800 ppm (total phenol basis) in CMC coating provided antioxidant protection to smoked eel, which increased with concentration. Additionally, the combination of the extract (200 ppm) with EO (2000 ppm) retarded significantly the formation of both primary and secondary oxidation products, indicating possible synergistic effects. The antimicrobial activity of EO and extracts was moderate, with the extract at 800 ppm concentration showing the best results in decreasing the rate of total viable count, Pseudomonas spp., and lactic acid bacteria growth.