Structural characteristics of wheat flour arabinoxylans = Structuurkenmerken van arabinoxylanen uit tarwebloem

H. Gruppen

    Research output: Thesisinternal PhD, WU

    Abstract

    <p>A procedure has been developed for the isolation of highly purified water-unextractable cell wall material (WUS) from wheat flour. From this material arabinoxylans were extracted via sequential extraction with Ba(OH) <sub>2</sub> , KOH and NaOH solutions. The first extract comprised arabinoxylans only, which represented 80% of all arabinoxylans present in the WUS. The arabinoxylans in this extract were fractionated using anion exchange chromatography and graded- ethanol precipitation. Neutral sugar and glycosidic linkage analysis revealed great similarities between these alkali-extractable arabinoxylans and similarly fractionated water-extractable arabinoxylans, isolated from the same wheat flour. Enzymic analysis using different endo-(1-4)- β-D-xylanases from <em>Aspergillus awamori</em> showed, however, that the water-extractable arabinoxylans were degraded both faster and to a larger extent than the alkali-extractable arabinoxylans.<p>Based on the structure and abundance of enzyme-resistant polymeric material and different oligosaccharides, the latter being identified with <sup>1</SUP>H-NMR analysis, present in the enzyme digests, a structural model is proposed for the arabinoxylans. This model shows that the arabinoxylan contains highly branched regions, interlinked with less branched regions which include subregions of unsubstituted xylose up to 7 contiguous residues. Variation in arabinose/xylose ratio between different arabinoxylan is due to variation in the relative proportion as well as the composition of the less branched regions. With increasing arabinose/xylose ratio of the arabinoxylans a decreasing extent of enzymic degradation observed. The enzymes used had different effects on the degradation of WUS and extracted arabinoxylans as well as on the baking performance of wheat flour.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    Supervisors/Advisors
    • Voragen, A.G.J., Promotor, External person
    • Hamer, Rob, Promotor
    Award date4 Dec 1992
    Place of PublicationS.l.
    Publisher
    Print ISBNs9789054850489
    Publication statusPublished - 1992

    Keywords

    • wheat flour
    • polysaccharides
    • cum laude

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