Effect of ultrasonic treatment on the total phenolic and antioxidant activity of extracts from citrus peel.

Application of ultrasound to extract a variety of biologically active compounds from plant materials has been widely investigated. However, there are few reports on the local effect of ultrasonic irradiation on the yields of these compounds. In the present article, the local effect of ultrasonic treatment on total phenolic content (TPC) and antioxidant activities (ATT) of extracts from citrus peels was investigated. To optimize the extraction process, a response surface methodology (RSM) was used to evaluate the effects of ultrasonic variables including ultrasonic power, ultrasonic time, and extraction temperature on extracts from penggan (Citrus reticulata) peel. The results showed that TPC and ATT increased on increasing ultrasonic time and temperature. The maximum of TPC and ATT by ultrasonic treatment was observed in near ultrasonic irradiation surface, in which ultrasonic power appeared to be positive effect. Furthermore, when the effect of the 3 independent variables was evaluated simultaneously using RSM, the optimal ultrasonic conditions for responses were determined as: 42 to 45 W, 23 to 25 min, 31 to 34 degrees C. The results presented here emphasized that application of ultrasound should be considered both the optimization of ultrasonic variables and available ultrasonic device.