Structural variability of arabinoxylans from wheat flour. Comparison of water-extractable and xylanase-extractable arabinoxylans

The structural variations in water-extractable arabinoxylans (WE-AX) and water-unextractable AX (WU-AX) in a collection of flours from twenty wheat (Triticum aestivum) cultivars was compared using sequential solubilization of the arabinoxylans first using water and then by treatment with a Trichoderma viride xylanase. The arabinoxylans were characterised by their relative proportions of mono-substituted xylose (mXyl), di-substituted xylose (dXyl) and un-substituted xylose (uXyl) WE-AX and xylanase-extractable arabinoxylans (XE-AX). The arabinose to xylose ratios (A/X) varied from 0.47 to 0.58 and from 0.51 to 0.67, for WE-AX and XE-AX, respectively. These ranges are statistically different (P<0.01), showing that XE-AX have different proportions of substitution compared to WE-AX. The average proportions of uXyl and mXyl for both populations were also significantly different; XE-AX had more mono-substituted and consequently less un-substituted Xyl than WE-AX; nevertheless the proportions of dXyl were not significantly different (P=0.79), in fact the correlation coefficient for A/X ratios for WE-AX and XE-AX for the same samples was r=0.78 (P<0.01), showing that the variation of structure observed for WE-AX reflected the structural variations in the WU-AX in the wheat flours 11.