Study On Preparation Of Dietary Fibre And Oligosaccharides From Wheat Bran And Their Physicochemical Characteristics

The technology of release soluble dietary fiber from wheat bran through alkali extraction and alcohol precipitation, preparation of oligosaccharides from wheat soluble dietary fiber by composite enzyme of xylanase and cellulose were investigated, and nature in this research. The main results were as follows:The composition of wheat bran was analyzed and found to be as follows:moisture 12.10%, lipid 3.21%, protein 15.00%, starch 17.41%, ash 4.38%, SDF 0.95%, IDF 54.67%, TDF 55.72%, soluble pentosan 0.64% and insoluble pentosan 17.4%.The wheat bran starch was enzymatic hydrolyzed by a-amylase and glucoamylase. The optimal conditions for a-amylase hydrolysis were:temperature 95℃, hydrolysis time 15min, enzyme added 240U/g. The optimal conditions for glucoamylase hydrolysis were: temperature 60 ℃, hydrolysis time 30min, enzyme added 10000U/g.Using alkaline protease to hydrolyze and establishing its optimal conditions: temperature 60℃, hydrolysis time 30min, enzyme added 0.2AU/g.Wheat bran used as raw materials, the technology of alkali extraction were studied in order to prepare soluble dietary fiber. By the response surface method (RSM) test, the optimum technological parameters of preparation were determined on the basis of single factor experiments; the optimum conditions were:ratio of solid to liquid 1:21(w/v), pH 11.75, temperature 85℃, time 2h and H2O2 concentration 0.45%. Under this condition, the yied of soluble dietary fibre would be reached 11.45%.The wheat bran soluble dietary fibre was enzymatic hydrplyzed by xylanase and cellulose to produce oligosaccharides. The optimal conditions were:pH 5.5, temperature 55 ℃, xylanase added 600U/g, cellulose added 313U/g, hydrolysis time 2.5h.Study the differences of physicochemical properties and morphology on the soluble dietary fibre and oligosaccharides. Soluble dietary fibre after xylanase and cellulose degradation, SEM observation showed that soluble dietary fibre was loose structure and sheet, the form of oligosaccharides was looser reticulate structure. LLS showed the spherical particle’s diameter of oligosaccharides was smaller than SDF’s. Expansive force, solubility, hygroscopicity, heat stability were improved. Moisture retention, oil absorption were reduced. The fluid properties of soluble dietary fibre and oligosaccharides were determined. Results showed that soluble dietary fibre and oligosaccharides of pseudoplastic fluid, belongs to the non-newtonian fluid.HPLC, GC, IR, UV analysised oligosaccharide’s structure. The results showed that the molecular weight of oligosaccharide was 1780D, and it did not contain nucleic acid, contain little protein, and was composed of Glc, Xly, Arab, Galac, Man.Texture analyzer determined the effect of soluble dietary fibre and oligosaccharide on the texture of noodles. Results showed that with the increase of adding amount of soluble dietary fibre and oligosaccharide, compared with the control, the hardness of noodles were decreased. After adding soluble dietary fibre, the hardness of noodles was higher than adding oligosaccharide. Compared with the control noodles, after adding soluble dietary fibre and oligosaccharide, the indicators gumminess, springiness were no significant changes, and the chewiness of noodles made of soluble dietary fibre was no significant change, the chewiness of noodles made of oligosaccharide was decreased.