title: Variability in the structure of rye flour alkali-extractable arabinoxylans.
abstract: The variability in rye flour alkali-extractable arabinoxylan (AE-AX) structures was examined by extensive fractionation and enzymic degradation studies. AX were isolated from destarched rye water-unextractables by sequential extraction with saturated barium hydroxide solution, water, 1.0 M sodium hydroxide, and water. The isolated AE-AX contained ca. 51% AX with an arabinose to xylose (A/X) ratio of 0.71. Fractionation of the isolated AE-AX by ethanol precipitation yielded a range of AE-AX fractions containing AX molecules with different A/X ratios and substitution patterns. Degradation of these structurally different AE-AX fractions by an Aspergillus aculeatus endoxylanase (XAA) and a Bacillus subtilis endoxylanase (XBS) resulted in AX fragments with various structural features. Further fractionation of the degraded AE-AX fractions by ethanol precipitation showed that a strong correlation exists between the structural features of the AX fragments, that is, average degree of polymerization (DP) of the xylan backbone, A/X ratio, and substitution pattern. Results indicated that the rye flour AE-AX consist of a continuum of structures rather than of two types of AX or two types of regions in the AX molecule.
authors.affiliation: Laboratory of Food Chemistry, Katholieke Universiteit Leuven, Kasteelpark Arenberg 20, B-3001 Leuven, Belgium.
authors.forename: Tiny
authors.initials: T
authors.lastname: Verwimp
authors.forename: Valerie
authors.initials: V
authors.lastname: Van Craeyveld
authors.forename: Christophe M
authors.initials: CM
authors.lastname: Courtin
authors.forename: Jan A
authors.initials: JA
authors.lastname: Delcour
mesh_terms: D043364:Endo-1,4-beta Xylanases / Q000378:metabolism; D005433:Flour / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D012434:Secale / Q000737:chemistry*; D012639:Seeds / Q000737:chemistry; D014990:Xylans / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D014990:Xylans; C085118:arabinoxylan; D043364:Endo-1,4-beta Xylanases