| The black-grained wheat refers to seed the darker color, blue, violet, purple, black and other colors wheat collectively, is currently the research institutions to adopt different method in breeding and cultivated special quality wheat. The black-grained bran is by-products of the black-grained processing, which is rich in non-starch polysaccharides, mainly pentosans, β-glucan and other cellulose and hemicellulose. At present, the black-grained is very rare in the world, the black-grained research is mainly focused on the black-grained flour Pentosans in preliminary studies, The black-grained bran pentosan research rarely reported.The paper takes black-grained bran as the research object, using high pressure assisted water extraction, alkaline extraction, enzyme extraction of different methods on the main non starch polysaccharides-pentosan were prepared, and by gas chromatography (GC), high performance liquid chromatography (HPLC), infrared spectrum analysis method, the system preparation of components of the relative molecular mass and monosaccharide composition analysis, and the hydrolysis were studied, as a theoretical basis and data base, for further study of black-grained bran on the structural and functional basis.1. Based on single factor experiment, the black-grained as raw material, orthogonal experiments on enzymatic extraction conditions were optimized. The optimized preparation conditions of non starch polysaccharides:enzyme dosage12mg/10g, extraction time2h, extraction temperature50℃,pH6. The rate of polysaccharide is4.17%under the conditions. The order of factors on the effect of Polysaccharide:enzyme concentration> extraction temperature> pH> extracting time. By gas chromatography (GC) and infrared spectroscopy (IR) on the basis of polysaccharides extracted from EEP monosaccharide composition analysis, the results showed that:EEP mainly containing monosaccharides as arabinose(Ara), xylose(Xyl), glucose (Glc) and trace amounts of galactose (Gal), in which Ara/Xyl ratios as of0.64.2. The black-grained bran polysaccharides were obtained by sequentially extracting the black-grained with water assisted by high pressure, saturated barium hydroxid, or distilled water as extraction medium respectively. Physicochemical properties were analyzed using instruments GC, HPLC, and IR. Results:The fractions extracted with water assisted by high pressure(WEPH)are mixture, which was the mixture of β-glucan and pentosan. The fractions extracted with saturated barium hydroxid (AEPH) are mainly composed of pentosan. The Ara/Xyl value is0.60, indicating relative pure pentosa. The fractions extracted with distilled water (AEPH-H2O) are composed of glucose and galactose, mainly β-glucan, arabino-galactan and minor part of pentosan. AEPH, which is rich in pentosan, has a high Mw of3.81×105, whereas WEPH and AEPH-H2O have relative low Mw.3. By0.02,0.1,0.2mol/L TFA on alkali extraction and component AEPH by partial acid hydrolysis, analysis on partial acid hydrolysis product of monosaccharide composition and determination of the relative molecular mass by gas chromatography. Results:trapped fluid AEPH-P0.02H, AEPH-P0.1H and AEPH-P0.2H Ara/Xyl ratios were0.47,0.24and0.21; the average relative molecular mass of AEPH-P0.1H and AEPH-P0.2H is8.03×104Da,1.31×104Da; the results showed that pentosan, mainly composed of Xyl and Ara sugar, as xylan for the backbone, Ara are connected to form the pentosan in the form of reducing end or oligosaccharide chain.4. Using pentosanase enzymatics on high-pressure water extraction component and alkali extraction, determination solution viscosity change on the condition of different enzyme dosage, different time. The results showed that:the amount of enzyme in different conditions, after water and alkali extraction its apparent viscosity decreased about57%and95%; in different conditions of time, after water and alkali extraction, its apparent viscosity decreased about76%and96%. |
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