Study On The Modification And Application Of Wheat Bran Dietary Fibre

The modification and application of wheat bran dietary were studied in this paper. The mixed enzymatic method was used to extract dietary fiber form wheat bran. Alcalase2.4L was selected as the optimal commercial protease to hydrolyze the wheat bran protein. Design-Expert analysis through central composite design experiments can draw the optimal preparation conditions: hydrolyzed the cohesive starch and protein in washed wheat bran under the conditions of pH 7.0, 68℃, Alcalase addition 4.32 AU/100g washed wheat bran,α-amylase addition 3440 U/100g washed wheat bran, hydrolyzing time 2.5 h. The purity of insoluble dietary fibre (DF1) was above 86%, the obtained ratio was about 39% and the extracted ratio was about 90%. The Infrared spectrum of DF1 showed the properties of polysaccharides, and the ultrastracture of DF1 was samall pieces.The optimal conditions of hydrolyzation on DF1 with xylanase were got from single factor experiments. In pH 5.0, addition 10 FXU xylanase per gram DF1, under the condition 55℃for 5 h, DF1 was hydrolyzed to get the xylanase hydrolysate of DF1(DF2) and soluble dietary fiber (DF3), and the interest rates of DF3 was 33%. The optimal conditions of hydrolyzation on DF1 with cellulase were got from single factor experiments also. In pH 4.6, addition 10 FXU cellulase per gram DF1, under the condition 50℃for 5 h, DF1 was hydrolyzed to get the cellulase hydrolysate of DF1 (DF4) and soluble dietary fiber (DF5), and the interest rates of DF5 was 30%. The physical, chemical and rheology properties of soluble dietary fibre were futher studied. The results showed that the monosaccharides composition of the soluble fiber (DF3 and DF5) were major in xylose, followed by Arabinose, glucose. Infrared spectrum indicated that there were significant feature of the sugar ester absorption peaks. Determination of the molecular weight distribution by HPLC showed their weight molecular was about 2340 Da. soluble dietary fibre was higher in solubility and lower in viscosity. The ultrastructure of DF3 and DF5 observed by scanning electron microscopy was different obviously. The ultrastructure of DF3 was loose network which was composed of irregular particles with the smooth surface structure and that of DF5 was irregular particles covered with a pattern like that of a honeycomb.The antioxidant activities of high fibre products from wheat bran were studied by the in vitro methods. The radical scavenging, reducing power, chelating ability, and antioxidation on linoleic acid were evaluated. The result showed that the processing of wheat bran to obtain dietary fibre concentrates withα-amylase and alcalase resulted in obvious losses of extractable phenolic (from 1239 to 179μg gallic acid equivalents/g) and the scavenging capacity on DPPH? (from 25.07 to 11.57μmol/g) and O2?- (from 110.63 to 46.4μmol/g), while insoluble dietary fibre hydrolysis with xylanase and celluase resulted in significant increase of scavenging capacity on OH? (from 30.23 to 60.97μmol/g), reducing power (from 12.90 to 18.32μmol ascorbic acid equivalents/g) and iron(II) chelating activity (from 4.89 to 17.03μmol EDTA equivalents/g) compared with wheat bran. All the products had the antioxidant capacity close to BHT (0.25 mg/mL) in a linoleic acid emulsion system. The antioxidant capacities of these fibre-rich products render them suitable products to be used in the preparation of functional foods.Influences of the dietary fiber (DF1 and DF2) upon the rheology properties of wheat dough with medium-gluten flour were investigated by a Brabender farinograph and an Extensograph. The studies emphasize the influence of the enzyme hydrolysis mechanism and the content of dietary fibre in wheat flour. Both DF1 and DF2 improved the farinogram to a certain extent. DF1 deteriorated the extensibility while DF2 improved it. The rheology properties were improved with the content of DF1 in the low level (2%～4%) and DF2 in the high level (2%～10%).The cooking and texture characteristics of noodles with DF1 and DF2 were also Studied. The results showed that cooking losses decreased as DF1 increased. Noodles made by 4% of DF1, was scored favourable and better than the control noodle by TA-XT2i texture analyser in hardness, gumminess and chewiness; Comprehensive evaluation of its content was from 2% to 4%. DF2 content was 6% and the cooking quality was better than the original noodles. However, all of the texture characteristics decreased of DF2 increased; Comprehensive evaluation of its content was from 4% to 6%.