Network Formation by Pilot Plant and Laboratory-Extracted Barley beta-Glucan and Its Rheological Properties in Aqueous Solutions

Barley and oat beta-glucans of low viscosity form reversible gels when prepared in sufficiently high concentrations. Solutions of three barley beta-glucan gums differing in molecular weight and thus in viscosity were prepared at 1.0, 2.5, or 5.0% (w/w) concentration levels. Medium- and high-viscosity gums were prepared in a pilot plant (PP) and laboratory (LAB), respectively. Low-viscosity (LV) gum was extracted in the laboratory at pH 7, which allowed for native enzymatic activity and decreased molecular weight. Network formation was monitored overnight through changes in storage (G') and loss (G") moduli. The strength of the formed network was determined from oscillatory rheological measurements by increasing the strain from 2 to 100%. Findings demonstrate that gelation of beta-glucan is molecular weight dependent and practically an instantaneous process for low-viscosity gum solutions at concentrations of less than or equal to 5% gum (or less than or equal to 4% beta-glucan), levels lower than previously anticipated. The purity of beta-glucan also seems to affect gelation rate. Better understanding of the beta-glucan gelation behavior is important for its functionality in both food product applications and physiological mechanisms of its health benefits.