STRUCTURAL CHARACTERISTICS OF THE WARM-WATER-SOLUBLE ARABINOXYLANS FROM THE TAILINGS OF THE SOFT WHEAT VARIETY KADET

Arabinoxylans were extracted from the tailings of the soft wheat variety Kadet with water at 70-degrees-C, and freed from protein by pronase digestion. The warm-water-soluble arabinoxylans, constituting 0.3% of the total flour, were fractionated by graded precipitation with ethanol and the four main fractions, covering 89% of the total, contained D-xylose and L-arabinose in a ratio ranging from 2.21:1.00 to 1.26:1.00. Methylation analysis and C-13-NMR spectroscopy revealed the arabinoxylans to consist of a (1 --> 4)-linked beta-D-xylopyranose-backbone substituted at O-3 or O-2,3 with terminal alpha-L-arabinofuranosyl residues. Differences in xylose to arabinose ratio were not only due to variations in the ratio unbranched to branched xylose, which ranged from 1.0 to 2.5, but also due to differences in the ratio 2,3,4-tri- to 3,4-di-substituted xylose, ranging from 0.4 to 2.1. Gel permeation chromatography revealed that the warm-water-soluble arabinoxylans consist solely of high-molecular-size material (> 40 kDa).