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

Abstract

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