2.2.3. D-Xylose including xylan and arabinoxylan
(K-XYLOSE 03/07, Megazyme).
Acid hydrolysis occurs in the presence of 1,3 M HCl. Interconversion
of the a- and b-anomeric forms of D-xylose is catalysed
by xylose mutarotase. The b-D-xylose is oxidised by NAD+ to Dxylonic
acid in the presence of b-xylose dehydrogenase at pH 7.5.
The amount of NADH which is measured by the increase in absorbance
at 340 nm.
In wheat flour the arabinoxylan to D-xylose ratio is 62%. This
factor was used to measure arabinoxylan in other samples.