Optimization of Enzymatic Extraction Process of Insoluble Dietary Fiber from Polygonatum sibiricum Residue by Response Surface Methodology and Its Characterization

The insoluble dietary fiber (HIDF) was extracted from Polygonatum sibiricum residue by response surface methodology. Firstly, the effects of solid-liquid ratio, papain concentration, papain hydrolysis time, α-amylase concentration and α-amylase hydrolysis time on the extraction rate of HIDF were discussed by single factor experiments, the extraction process parameters were optimized by response surface methodology (Box-Behnken). Finally, infrared spectrum analysis, X-ray diffraction and scanning electron microscope observation were carried out, the functional properties were determined. The results showed that the optimum extraction conditions were as follows: Solid-liquid ratio 1:20 mL/g, papain concentration 0.13%, papain enzymolysis time 1.9 h, α-amylase concentration 0.29%, α-amylase hydrolysis time 2 h, the content of HIDF was 52.184%. The hydraulic holding capacity, oil holding capacity and swelling capacity of HIDF were 5.99±0.05 g/g, 3.965±0.04 g/g and 4.565±0.05 mL/g, respectively. Therefore, HIDF extracted from Polygonatum sibiricum residue had good physical and chemical properties and was suitable for processing into functional food, which provided a reference for improving the utilization rate of Polygonatum sibiricum residue and further excavating its nutritional value.