Optimization of ultrasonic extraction conditions of polyphenols from walnut green husk by response surface methodology

The walnut green Husk as raw material, response surface methodology was used for optimization of process conditions of ultrasonic extraction of polyphenols. On the basis of single factor experiments, ultrasonic temperature, ultrasonic power and liquid-solid ratio were selected as significant influencing factors for achieving the maximum extraction rate. Using central composite design and response surface methodology, the optimum extraction conditions were ultrasonic power of 670 W, ultrasonic temperature of 57 ℃, liquid-solid ratio of 21:1(mL:g), ultrasonic time of 5 s, ultrasonic clearance time of 5 s, ultrasonic whole time of 25 min and stirring speed of 400 r/min. Under these conditions, the extraction rate was up to 55.473 mg/g.