Evaluation of the effect of ultrasonic variables at locally ultrasonic field on yield of hesperidin from penggan (Citrus reticulata) peels

• A three-level three-factor Box–Behnken design was applied.
• The parameters and their levels are: ultrasonic power (4-56, W), extraction time (10-40, min) and temperature (20-40, ºC).
• The yield of hesperidin at high and low ultrasonic irradiation surface was evaluated.
• The cell structure of penggan peel was observed by scanning electron microscopy.

It has been reported that the maximum ultrasonic power depended on the distance of ultrasonic irradiation surface. Therefore, to confirm this point, an experiment for ultrasound-assisted extraction (UAE) of hesperidin from penggan peels at locally ultrasonic field was performed by response surface methodology (RSM). A three-level three-factor Box–Behnken design was applied to evaluate the effects of three independent variables including ultrasonic power, extraction time and temperature on the yields of hesperidin at high and low ultrasonic irradiation surface. The results showed that the coefficients of two mathematical-regression models by means of the second-order polynomial equation obtained at high and low ultrasonic irradiation surface was 0.9742 and 0.9745, respectively, thus indicating that quadratic polynomial model could be used to estimate the ultrasound-assisted extraction of hesperidin. By comparison of the ultrasonic irradiation surface influence, the yield of hesperidin obtained at low ultrasonic irradiation surface was much higher than the high ultrasonic irradiation surface. Moreover, the scanning electron microscopy (SEM) showed that the particles' microstructures of Penggan peel obtained at low ultrasonic irradiation surface were destroyed more heavily than high ultrasonic irradiation surface. As a result, the vicinity of ultrasonic irradiation surface can generate stronger cavitation energy.