| Nowadays, wheat and wheat malts are commonly used as main material in the brewing industry of beer. Arabinoxylans(AX), which is a cell wall non-starch poly-saccharideds, is mainly constituent in cereals as wheat, rye and barley. AX affects theviscosity, turbidity and filtration velocity of malt and beer; also, AX plays an important role in the foaming property, mellowness, turbidity of beer. It was also found that water-extractable AX(WEAX) generally improves the quality of flour product. Adding WEAX in flour could increase the water holding capacity and mechanical strength of dough, reduce the diffusion rate of CO2, improve the stability of the bubbles and the composite structures of the dough, prolong the time for dough to rise, and increase the volume of the baked dough. Wheat cereal contains 1.5 ~ 2.5% AX; however, the content of AX in bran is as high as 20% ~ 25%. Since degrading the AX requires an effective enzyme system, endo-β-(1,4)-D-xylanase, as the most efficient enzyme in the system, is applied in the study. This study is to apply the wheat bran as the material to extract WEAX by water and ethyl alcohol based on different processes. The effects of extraction time, temperature, and ratio of solid to liquid on the yield of WEAX extraction and the effects of additions of adsorbing gel, ethanol concentration on the purification of WEAX are also studied. Furthermore, the influences of purification with different additions of adsorbing gel and concentration of alcohol for precipitation were determined. In addition, the research is also on the track of enzymatic hydrolysis reaction of WEAX. The endoxylanase from wheat malt was applied to degrade the WEAX from wheat bran, while the degradation of WEAX was determined by structural analysis. The major found results are listed as below:(1) In this study, the aim is to optimize the extraction and purification methods for obtaining WEAX from wheat bran.The result showed that the optimal method for extraction of WEAX was in water at high degree at 55℃ for 90 minutes, ratio of solid to liquid was 1: 6 on a rolling boil for 10 minutes. After centrifugation, the gel was added based on the amount of protein(mprotein:mgel = 1: 200). The component of ehanol precipitation has higher yield of WEAX by 85% alcohol.(2) WEAX was analysed by by gas chromatography and gel filtration chromatography. The monosaccaride composition of the purification products suggested that the content of WEAXs was 70.89%, A/X ratio was 0.44, molecular weight of WEAXs was mainly distributed in 6.20 × 105 Da, 7.88 × 104 Da and 1.8 × 104 Da, with the account of 31.56%, 27.93% and 31.81%, respectively.(3) Enzymatic hydrolysis of WEAX was analysed. 0.1 mg/m L endoxylanase was added into 10 mg/mL WEAX for enzymatic hydrolysis, reacted under condition of 45℃ and pH of 7.0, boiling after 3-hour reaction, keeping in cold-storage under-20℃ for next analysis. The solution viscosity of blank control group without enzyme was 1.24 ± 0.03 mPa·s. The monosaccaride composition of the blank group suggested that the A/X ratio was 0.44, molecular weight of WEAX was main distributed in 3.97 × 105 Da, 7.89 × 104 Da, and 2.02 × 104 Da, with the account of 31.56%, 27.93% and 31.81%, respectively;nevertheless, the solution viscosity of experimental group with enzyme was 1.15 ± 0.02 mPa·s, Mw mainly distributed in 8.74 × 104 Da, 2.49 × 104 Da, 1.35 × 103 Da, with the account of 59.91%, 18.46%, and 15.10%, respectively. After enzymic degrading, the viscosity of WEAX was going down significantly and the WEAX with molecular weight of 104 was decreased efficienctly. |
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