Correlation between arabinose content and the conformation of arabinoxylan in water dispersions

Arabinoxylan (AX) with varying arabinose to xylose (A/X) ratios of 0.85, 0.57 and 0.39 was extracted from wheat bran, and the conformations of the AX polysaccharides dispersed in water were investigated using small-angle X-ray scattering. The persistence length (L_p) and the conformation statistics (expressed by the Flory exponent v or the mass fractal) of the AX varied with their A/X ratios. The L_p decreased with decreasing A/X ratio, from 4.5 nm to 1.5 nm, where the AX with high and intermediate A/X ratios can be considered semi-flexible chains, while AX with the lowest A/X ratio behaves as a flexible chain. The mass fractal increased from 1.7 to 2.5 between the highest and lowest A/X ratios, indicating increasingly compact polymer conformations. AX with the highest A/X ratio behaved as chains in a good solvent and was well dispersed even in the semi-dilute regime. AX with intermediate and low A/X ratios showed stronger tendencies to aggregate and were not well dispersed at higher concentrations. The results presented show that the macroscopic properties of AX dispersions can be understood based on the chemical composition and fine structure of the AX polysaccharide.