Fractionation, physicochemical and structural characterization of polysaccharides from barley water-soluble fiber

Glucans of multiple architecture and bioactivities are widely distributed in cereals. In our previous study, the barley water-soluble fiber (BSF) has been proved to possess hypoglycaemic and hypolipidaemic effects. A further attempt in the present study is to comprehensively demonstrate the structures and solution properties of main constituents in BSF. Two mainly homogeneous fractions (BSF-20 and BSF-80r) were purified from BSF, and their physicochemical and structural characterization were investigated. Methylation and 1D/2D NMR experiments indicated that BSF-20 was a linear β-glucan, composed of β-D-Glcp residues via (1 → 4)-linkages, and occasionally single (1 → 3)-linkage. The high performance size-exclusion chromatography coupled with multiangle laser light scattering, X-ray diffraction, rheological measurements and scanning electron microscopy were further conducted to analyze its solution property and morphology. BSF-20 adopted a linear flexible chain in aqueous solution, and exhibited high viscosity and strong gelling properties. Intertwined fibrous filaments were visualized by SEM observation. Besides, BSF-80r was a limit dextrin, which was an artefact caused by the incomplete hydrolysis of starch during the isolation of barley soluble fiber. Therefore, the highly viscous β-glucan is the main biomacromolecule occurring in BSF. This work lays the groundwork for the potential application of barley soluble fiber in beverages and other liquid products as new thickeners and stabilizers.