Optimization of ultrasonic treatment of rose myrtle mash in the extraction of juice with high antioxidant level

Phenolic compounds and ascorbic acid are main antioxidants in rose myrtle (Rhodomyrtus tomentosa) fruit. In this study, ultrasound was applied to the treatment of fruit mash for juice extraction. The effects of ultrasonic power and time on the level of total phenolics and ascorbic acid in the rose myrtle juice were investigated. Ultrasonic treatment significantly improved both antioxidant content and activity of the extract. Response surface methodology was then used to optimize the sonication conditions for maximizing the antioxidant activity of the juice. The optimal ultrasonic power and time were 25 W/g and 6.5 min, respectively under which the concentration of total phenolics and ascorbic acid in the extract achieved 6,067 mg gallic acid equivalent (GAE)/L and 516 mg/L, respectively. In the ultrasound-assisted extraction, the maximal antioxidant activity of the rose myrtle juice evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) method was 24.76 mmol Trolox equivalent antioxidant capacity (TEAC)/L and this value was 86% higher than that in the control sample.