Optimization of Microwave Extraction ofPolysaccharides from Stigma Maydis by CentralComposition Design

Polysaccharides extraction from Stigma Maydis was carried out using microwave- directed. The Plackett-Burnam design was applied to screening the key factors which would affect the yield of Stigma Maydis polysaccharides extracted. Key factors were microwave-directed extracting temperature, extracting power, and liquid-solid ratio. The path of steepest climbing was used to approach the optimal region of the extraction condition, and the experiment parameters were further optimized using central composite design and response surface analysis, the optimized condition was obtained. The statistical analysis of the experiment indicated that the extracting temperature, the power had significant effect on the polysaccharides yield. The central composite design showed the polynomial regression models were in good agreement with the experimental results for the polysaccharides yield. The optimized condition for polysaccharides yield within the experimental range of the variables studied was extracting temperature 85 °C, power 400 W, liquid-solid ratio 80mL/g, time 15 min. At this condition, the predicted polysaccharides yield was 8.93±0.43%, the real value was 9.36±0.22%, and the relative deviation between the predicted valued and real value was less than 0.5%.