Antioxidant capacities and betacyanin lc‐ms profile of red‐fleshed dragon fruit juice (hylocereus polyrhizus) extracted by ultrasound‐assisted enzymatic treatment and optimized by response surface methodology

For the enhancement of betacyanin and phenolic compounds, that is, health‐beneficial antioxidants, in red‐fleshed dragon fruit, the response surface methodology (RSM) was employed using the Box–Behnken design to determine the combined effects of ultrasonic and enzymatic treatments on the maximization of their contents in the fruit juice. The optimal condition including 18.4 min of sonication and 88.5 min of enzymatic treatment at 33.0°C was obtained for the highest release of betacyanins, while those values were 13.4 min, 71.5 min, and 43.9°C, respectively, for the optimal total phenolic content (TPC). Liquid chromatographic and mass spectrometric (LC‐MS) analysis and antioxidant tests by 2,2‐diphenyl‐2‐picrylhydrazyl hydrate (DPPH) and ferric reducing antioxidant potential (FRAP) assays verified that the optimization of ultrasound‐assisted enzymatic treatment process toward betacyanin could improve the release of native betacyanins and betalain‐related compounds. Meanwhile, although TPC‐aimed optimization led to moderate degradation of native betacyanins, it enhanced the overall antioxidant capacities of the juice more efficiently. Practical applications Dragon fruit has high contents of betacyanins and phenolics which are health‐benefit bioactive compounds. The combination of ultrasonic and enzymatic treatment is one green extraction technology to enhance these compounds into the juice. Response surface methodology (RSM) with Box–Behnken design can reduce the number of experiments and provide the optimal operating parameters for the system. The results of the current work could provide useful data for pilot and industrial scale‐up applications.