Rheological properties of aqueous solutions of (1 leads to 3) (1 leads to 4)-beta-D-glucan from oats (Avena sativa L.).

Abstract

The rheological behavior of partially hydrolyzed oat (1→3)(1→4)-β-D-glucan was compared to that of the original unhydrolyzed β-D-glucan. Flow and oscillatory shear measurements of the nonhydrolyzed sample in aqueous solution showed behavior typical of noninteracting polysaccharides, such as guar gum, in solution. The rheology of partially hydrolyzed samples shifted toward the more get-like behavior observed with polymers, which tend to aggregate and form a three-dimensional macromolecular network. The aggregation may arise from a tendency of the β-glucan to self-associate through cellulose-like sequences in the structure. However, the reason why this behavior was not observed with unhydrolyzed oat gum is not understood. It is unlikely that structural variations, such as the amount of cellulose-like sequences, accounted for the different rheology, because quantitative analysis of oligosaccharides released by lichenase evidenced only minor differences between intact oat β-glucan and hydrolyzed samples. A more likely explanation is that because of their lower molecular weight, the partially hydrolyzed molecules are more mobile and diffuse more easily. Hence, they have a greater probability of forming aggregates.