Studies On Extraction,Purification,Structure Identification And Function On Polysaccharides From Sweet Potato Residue

Sweet potato occupies a place in my country's food by virtue of high nutrition and high medicinal effects.It has good development advantages.The sweet potato industry came into being,and at the same time,new products were born.However,after a series of complicated processes,the by-product-sweet potato dregs was inevitably treated as discards.There were few studies on sweet potato residue polysaccharides produced by traditional techniques.This research mainly uses response surface optimization to compare the yield of sweet potato residue polysaccharides by water extraction and alcohol precipitation method and ultrasonic-assisted water extraction method.After a series of separation and purification,the purity was identified,and its structure was analyzed to determine its in vitro antioxidant activity,in vitro hypoglycemic function,and ability to eliminate nitrite and block the synthesis of nitrosamines.The specific research results are as follows:1.Polysaccharide extraction:The ratio of material to liquid is 1:30(g/m L),the extraction time is 5.5 h,and the extraction temperature at 80°C.The average yield of polysaccharides from sweet potato residue by water extraction and alcohol precipitation is 5.614%.With a material-to-liquid ratio of 1:17(g/m L),ultrasonic time of 57 min,ultrasonic power of 209 W,and ultrasonic temperature at 60°C,the average yield of sweet potato residue polysaccharides by ultrasonic-assisted water extraction was 5.926%,which was higher than the former 0.312%.2.Separation and purification:The Sevag-enzymatic method has a significant effect on the deproteinization of sweet potato residue polysaccharides,which removes 76.41%of protein and only loses 25.69%of sweet potato residue polysaccharides.For the decolorization of sweet potato dregs polysaccharides,the H₂O₂ method is effective,the decolorization rate is 82.71%,and the polysaccharide loss rate is 30.03%.After 72 hours of dialysis treatment,DEAE-52 cellulose column chromatography graded SPRP-1,SPRP-2,and SPRP-3.Since the content of SPRP-2 and SPRP-3 is small,they will not be considered later.Then it was identified that the sweet potato residue polysaccharide was a pure polysaccharide.3.Structure determination:The relative molecular mass of sweet potato residue polysaccharide determined by Ubbelohde viscometer method is2.04×105g/mol.The result of high performance liquid chromatography showed that the molar ratio of monosaccharide of sweet potato residue polysaccharide was mannose:rhamnose:glucose:galactose:xylose=7.34:1.08:11.56:15.14:1.The results of infrared spectroscopy showed that the sweet potato residue polysaccharides contained pyran rings and belonged to?-type and D-type glucose.The sweet potato residue polysaccharide obtained by the Congo red experiment does not belong to the triple helix structure.Scanning electron microscopy observed that the sweet potato residue polysaccharides had a flaky structure with layers of fractured surfaces.Atomic force microscopy observed the existence of two types of polysaccharide chain structures:rod-like and thin-chain structures.4.In-vitro functional evaluation:The antioxidant activity of sweet potato residue polysaccharides was preliminarily discussed from the results of reducing power,DPPH·,·O-2,·OH,ABTS⁺·,by inhibiting?-glucosidase and?-amylase.Enzymes were used to investigate the in vitro hypoglycemic function of sweet potato residue polysaccharides,and to analyze the ability of sweet potato residue polysaccharides to remove nitrite and block the synthesis of nitrosamines.The results showed that the antioxidant capacity of sweet potato residue polysaccharides was slightly lower than that of Vc,and the IC₅₀ for the clearance rates of DPPH·,·O-2,·OH,ABTS⁺·were29.928?g/m L,0.308 mg/m L,0.537 mg/m L,0.881 mg/m L,respectively.The IC₅₀ of the sweet potato residue polysaccharide on the inhibition of the two enzymes was 1.116 mg/m L and 1.326 mg/m L,respectively,which was slightly inferior to Acarbose.When the mass concentration of sweet potato residue polysaccharide is 2mg/m L,it can remove 81.02%of nitrite and block 81.63%of nitrosamine synthesis.