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Solubilization and Structural Characterization of Arabinoxylans from Wheat Bran A. MENSE (1), Y. Shi (1) (1) Kansas State University, Manhattan, KS, U.S.A..
Wheat bran was dissolved using a novel solvent to elucidate structural and chemical composition information. This dissolution procedure was to dissolve a majority of the wheat bran and preserve the structural integrity of the dissolved polymers. Structural and chemical information from both the dissolved and undissolved fractions were reported. The structure of the extracted non-starch polysaccharides were investigated using a 12% urea and 7% sodium hydroxide solvent. The extraction procedure involved the repeated cooling of the solvent bran mixture to -12.6°C and then agitating it at 25°C. When this procedure was applied to wheat bran, 84.14% was solubilized. Ethanol precipitated solubilized bran material, which was 43% of the bran, had an A/X ratio of 0.93. The undissolved fraction was constituted of 9% of the original bran arabinoxylan with an A/X ratio of 1.04 and 59% cellulose. These A/X ratios are similar to those found in the bran pericarp layer. The unextractable AX in the undissolved bran fraction was composed of highly branched arabinoxylan possibly physically and/or chemically linked to other cell wall components. The molecular weight range of the precipitated bran material was 3,420,267-43,495. The molecular weight was confirmed by using a pullulan standard. The average molecular weight of the precipitated bran material was 620,026. This procedure dissolved wheat bran while preserving high molecular weight polymers for structural characterization. Knowledge of wheat bran structure will increase our understanding of the factors that effect bran solubility, mechanical properties, and processing.
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