Essential oil of Aloysia triphylla in Nile tilapia: anaesthesia, stress parameters and sensory evaluation of fillets

Abstract

The optimum concentration of anaesthetic used to facilitate fish handling can be determined based on induction and recovery time, among other factors. This study aimed to evaluate the effectiveness of the essential oil of Aloysia triphylla (EOAT) as an anaesthetic in the handling of Nile tilapia juveniles. Nile tilapias exemplars were immersed at 0 (control group), 10, 20, 30, 40, 80, 150, 300 and 450 μL L−1 EOAT to evaluate sedation, anaesthesia and recovery time. The stress response was evaluated by the determination of plasma glucose, cortisol, lactate and paraoxonase levels in anaesthetized (300 μL L−1 EOAT) and non-anaesthetized fish. Fillets from both groups were evaluated for organoleptic characteristics (taste and odour). Concentrations of 80–450 μL L−1 EOAT were effective in inducing anaesthesia. There was a significant reduction in plasma cortisol levels one hour after handling in individuals anaesthetized with 300 μL L−1 EOAT compared to the control group. Tasters did not detect differences in fillet taste and odour between fish exposed and not exposed to EOAT. A concentration of 300 μL L−1 EOAT is recommended for handling Nile tilapia because it presents good anaesthetic induction and recovery times, causes a reduction in plasma cortisol levels one hour after handling and does not affect the taste or odour of the fillets.