2.5.2. Response surface methodology
The oligosaccharides content was further optimized through the response surface methodology (RSM) approach. Based on the results of the single factor experiments, ranges of the three factors,solvent concentration (X1), ultrasound time (X2) and ultrasound temperature (X3) were determined. The experiments were designed to evaluate the effect of these factors on the yield of oligosaccharides using ultrasound extraction method (Table 1).Predicted response values for the total oligosaccharide concentration were obtained using Box–Behnken Design (BBD). The mathematical model representing the concentration of oligosaccharides as a function of the independent variables within the range studied was expressed as follows: