The Study On Modification Of Dietary Fiber From Sweet Potato Residue By Steam Exlosion

There was a large amount sweet potato planted in China,aboout 4.1 million hectares of land planted sweet potato every year and 80% of sweet potato production.Sweet potato is not only used to eat or as the main raw material in food processing,but as the material to product starch or sweet potato concentrated juice.However,the sweet potato residue is the by-product.Sweet potato residue contains extremely rich dietary fiber.About 10 million tons of sweet potato residues were generated in China every year.Unfortunately,the utilization rate of sweet potato residue is very low.A large part of sweet potato residue was thrown but little part was used to product animal feed.The situation hads not only polluted the ecological environment,but caused the dietary fiber waste.Dietary fiber had the virtue of preventing constipation,colon cancer,cardiovascular disease,eliminating exogenous harmful substances.Results showed dietary fiber,especially soluble dietary fiber content in sweet potato residue increased significantly after modified by steam explosion.Sweet potato residue was as the research object,steam explosion treatment of sweet potato residue conditions were optimized by response surface methodology to get the largest soluble dietary fiber content.The main contents in the research included physicochemical,functional,structural properties,farinograph properties of wheat flours replaced with increasing quantities,and the sensory evaluation of cookie with increasing quantities of sweet potato residue modified by steam explosion.The main results were as follows:1.Seven varieties of sweet potato residue were selected(xushu22,baizheng2,baizheng3,shangshu19,xushu55,jishu5,jishu50).The content of major nutritional components,mineral elements,dietary fiber and amino acids were determined.Results showed that the content of dietary fiber(42.73%)and protein(6.23%)in shangshu19 are most among the seven varieties of sweet potato residue,yet the content of fat in shangshu19 is least,so it could as a good resource to reuse.2.Sweet potato residue was modified by steam explosion,steam pressure,residence time,sieving mesh sizes as the independent variable.The content of soluble dietary fiber as the dependent variable,the optimal conditions were as follows: steam pressure of 0.35 MPa,residence time of 121 s,and sieving mesh of 60.the content of soluble dietary fiber from the sweet potato residue modified by steam explosion could reach 22.75% On this conditions.3.The soluble dietary fiber was extracted after the optimal steam explosion conditions treated.The physicochemical,functional and structural properties of soluble dietary fiber were determined.Studies have shown that the water holding capacity(3.51~5.17 g/g),oil holding capacity(1.23~2.43 g/g),swelling capacity(2.44~3.43 g/g),glucose adsorption capacity(2.99~7.55 mmol/g),?-Amylase activity inhibition ration(25.26~40.32%),pancreatic lipase activity inhibition ration(13.17~21.49%),cation exchange capacity(0.33~0.92 mmol/g)all were improved after the steam explosion.The result of FT-IR spectroscopy,X-ray diffraction and scanning electron microscopy shown that the steam explosion made its cellular structure fracture,but had little influence on its chemical component.4.The result of farinograph properties of plain and strong wheat flours replaced with increasing quantities of sweet potato residue modified by steam explosion as follows: wheat flours replaced with increasing quantities of sweet potato residue modified by steam explosion,the wheat gluten was diluted.The sedimentation value,falling number,peak viscosity,trough viscosity,final viscosity,breakdown and setback viscosity were significantly decreased.Moreover,the level of the sweet potato residue increasing modified by steam explosion added in the blends increased resulted in a decrease in development time,stability time and farinograph quality number and an increase in water absorption,softness values.After the sweet potato residue modified by steam explosion level added in the blends increased,the texture properties of cookie had changed,according to the sensory evaluation of cookie,the cookie with 6 % sweet potato residue modified by steam explosion had the better sensory acceptability,score for 91.3.A certain amount of sweet potato residue modified by steam explosion was added in the cookie in order to supplement the dietary fiber.