The Studies On Extraction, Purification And Properties Of Purple Sweet Potato Non-starch Polysaccharide

In this paper, purple sweet potato which is nutritional and high in medicinal valuewas taken as the research object the extraction and separation process of the purplesweet potato polysaccharide were studied. And then antioxidant activities and stabilityof purple sweet potato polysaccharide extracted were analyzed in vitro; thepolysaccharide purple sweet potato was further purified by Gel filtrationchromatography. Scanning electron microscope, X-ray diffraction and Differentialscanning calorimetrywere applied for analyzing the solid state characteristics of crudeand purified polysaccharide. The main research results were as follows:The determination of main ingredients in purple sweet potato: moisture content58.42%, protein content7.57%(dry base), crude fat0.34%(dry base), starch34.17%(wet base), total sugar2.73%(extraction conditions:40℃,extracted3h), reducingsugar1.43%(extraction conditions:40℃,extract3h).The extraction of Purple sweet potato polysaccharides: rate of polysaccharideobtained was taken as the index, traditional method by hot water andmicrowave-assisted methods were compared. In the optimum conditions, the rate ofpolysaccharide obtained was2.73%for traditional method, and was5.75%for the latter.Microwave extraction method was selected.The separation of purple sweet potato polysaccharide: Deproteinization anddecoloring of polysaccharide was investigated. Deproteinization effects of threedifferent methods (Sevage, TCA, ammonium sulfate) were compared, and optimizeddeproteinization conditions by orthogonal experiment, deproteinization rate was80.75%,polysaccharide loss rate was25.98%on the optimum condition. Decoloring of thepolysaccharide extraction by active carbon, optimized by orthogonal experiment,decoloration rate was86.48%and polysaccharide loss rate was5.57%.The purification of polysaccharide: crude polysaccharide extracted was purified bySepharose Cl-6B, and properties of polysaccharide purified were analyzed. Afterpurification, collected ppsp1, ppsp2, ppsp3respectively according to descending orderof molecular weight, pspp1composed of protein was white floe non-starchpolysaccharide, pspp2and pspp3were white non-starch pure polysaccharide.The study of antioxidant activities in vitro and stability of purple sweet potatopolysaccharide: antioxidant activities of freeze-drying and vacuum drying crude polysaccharide were compared. Results showed that, activities of freeze-dryingpolysaccharide was prior to vacuum drying ones, but were both less than Vc. Influencesof PH value, temperature, lighting conditions on stability of crude polysaccharidesolution were discussed, storing at neutral or alkaline pH value, below45℃and undernatural light or dark was helpful for the stability.Solid features of purple sweet potato polysaccharide: protein content of crudepolysaccharide was13.07%,17amino acid were included; infrared analysis indicatedthat pspp1, pspp2and pspp3contained a-glucosidic bond; pspp1, pspp2containedD-pyranoid keys, pspp1contained protein; scanning electron microscope, X-raydiffraction and DSC analysis showed that vacuum drying and freeze-dryingpolysaccharide were very different in aggregation state and thermal stability.