The FT-IR fingerprint of wheat endosperm arabinoxylan (AX) was investigated using a set ofpolysaccharides exhibiting variation of their degree of substitution and xylo-oligosaccharides comprisingxylose units mono- or disubstituted by arabinose residues. Substitution of the xylose backbone byarabinose side units was more particularly studied in the 1000-800 cm
-1 spectral region, by takingadvantage of second-derivative enhancement. The 920-1020 cm
-1 spectral region revealed twoabsorption bands at 984 and 958 cm
-1, the intensities of which varied according to the degree ofsubstitution. Whereas the intensity of the band at 958 cm
-1 increased with the degree of substitution,that at 984 cm
-1 decreased. The second-derivative spectral data of xylo-oligosaccharides indicatedthat these changes could be attributed to substitution of the xylan backbone by arabinose residues,and the band at 958 cm
-1 was ascribed to the presence of disubstituted xylose residues. Principalcomponent analysis of FT-IR spectra of model mixtures of AX,
-glucans, and arabinogalactanssuggested that it is possible to evaluate the relative proportions of the polymers and degree ofsubstitution of AX in complex mixtures such as the cell wall of cereal grains.Keywords: Hemicellulose;
-glucan; arabinogalactan; pentosan; wheat; principal component analysis