Asymmetrical flow field-flow fractionation enables the characterization of molecular and supramolecular properties of cereal beta-glucan dispersions

In this paper we study the properties of molecular and supra molecular species in cereal beta-glucan solutions/dispersions by the utilization of asymmetrical flow field-flow fractionation coupled to multi-angle light scattering and refractive index (AsFIFFF-MALS-RI) detectors. The samples were purified barley and oat beta-glucans which were dissolved in aqueous solution using either mild conditions or more harsh treatments with alkali. Dissolution in 0.5 M NaOH was not sufficient to eliminate aggregated structures in barley beta-glucan. The results in this paper show how distinction can possibly be made between molecular and supra molecular species using scaling approaches and conformational parameters obtained from AsFIFFF-MALS-RI over the entire size distribution. Small species in the barley beta-glucan samples display properties ranging from elongated conformation to random coil conformation. Aggregates have low apparent densities and a swollen micro gel structure. Oat beta-glucan displays no properties that can be attributed to a molecularly dissolved beta-glucan showing that dissolution was incomplete. The aggregate properties analyzed were similar between oat and barley beta-glucan.