Optimisation of ultrasound-assisted extraction of carotenoids and antioxidant activity from Citrus reticulata Blanco peels (Wilking mandarin)

A large amount of waste, especially the outer part of citrus fruits (peel), is generated after consuming the pulp and it remains unused. The valorisation of this waste by recovering its bioactive compounds seems interesting. The aim of this study was to find the optimal conditions using ultrasound-assisted extraction (UAE) that yield the highest carotenoid content and better antioxidant activity from Citrus reticulata Blanco peels.Response surface methodology (RSM) through Box–Behnken experimental design was used to optimise the conditions for carotenoid extraction using UAE. Hexane concentration, temperature, and sonication time were selected as the main factors.The results revealed that all independent variables affected the responses. The optimal UAE conditions for hexane concentration, temperature, and sonication time were 60.76%, 36.45 °C, and 37.32 min, respectively. The values of total carotenoid content (TCC) and total antioxidant activity (TAA) obtained by UAE were higher than those obtained by the maceration extraction method.It can be concluded that the medium and extraction parameters, including hexane concentration, temperature, and sonication time, significantly influenced the recovery of carotenoids and antioxidant activity. The optimisation study allowed determining the appropriate conditions to maximise both responses. Compared to conventional maceration, the UAE method was superior and more efficient for extracting carotenoids from C. reticulata Blanco peels.