Optimization of microwave-assisted extraction technology of stevioside from Stevia rebaudiana Bertoni leaves by response surface analysis

The effect of liquid to material ratio, microwave processing time and microwave power on extraction rate of stevioside in leaves of Stevia rebaudiana Bertoni were studied by single-factor experiments.On the basis of single-factor experiments, a quadratic polynomial regression equation of the forecasting model was set up using Box-Behnken design of three factors and three levels.The optimal conditions of microwave-assisted extraction were concluded as follows:liquid to material ratio 22:1 (mL:g) , microwave treatment time 12min, microwave power 500W.The actual detection value of stevioside extraction rate was 90.6mg/g, which was almost equal to the predictable value.