Distribution and structural variation of arabinoxylans in common wheat mill streams

In 19 wheat-milling fractions total pentosan content, calculated as 0.88 x (% L-arabinose + % D-xylose), varied between 1.44 and 30.66% on dry matter (dm). It increased with ash content once the latter exceeded 0.6% (dm basis ). Water-extractable arabinoxylans were recovered by saturating water extra cts to 65% ethanol. Their contents in the milling fi actions varied between 0.35 and 1.38%, and above 0.6% ash content also increased with this parame ter. Their L-arabinose-to-D-xylose ratios ranged between 0.65 and 0.39, wit h the lowest values found for the fractions with highest ash content, indic ating that the ash-rich tissues contain more arabinoxylans that are less br anched. H-1 NMR spectroscopy revealed that the decrease in L-arabinose-to-D -xylose ratio was accompanied by an increase in unsubstituted xylose residu es and a decrease in disubstituted xylose residues, while the contents of m onosubstituted xyloses were virtually constant.