Optimization of Ultrasound-Assisted Extraction Procedure to Determine Total Isoflavones in Chinese Soybean Cheese by Box–Behnken Design

Abstract

Isoflavones from Chinese soybean cheese were extracted with aqueous ethanol. Single-factor experiment design was employed to optimize the solid-to-liquid ratio (in grams per milliliter), ethanol concentration (in percent), extraction time (in hours), and extraction temperature (in degrees Celsius). The solid-to-liquid ratio was 1.5:10 (g/mL), and ethanol concentration (50 %–90 %), extraction time (2–3 h), extraction temperature (50–70 °C) were used for further optimization of extraction conditions. The optimal conditions for the ultrasound-assisted extraction of total isoflavones from Chinese soybean cheese were determined using response surface methodology (RSM) by Box–Behnken design. Three variables “ethanol concentration, extraction time and extraction temperature” were regarded as factors in the optimization study. The optimal conditions for total isoflavone extraction in Chinese soybean cheese were: ethanol concentration of 65.43 %, extraction temperature of 65.38 °C, and extraction time of 2.51 h. The verification experimental OD value was 0.534, which agreed with the predicted value, thus indicating suitability of the model employed and the suitability of RSM in optimizing the extraction conditions.