RHEOLOGICAL PROPERTIES OF AQUEOUS-SOLUTIONS OF (1-]3)(1-]4)-BETA-D-GLUCAN FROM OATS (AVENA-SATIVA L)

The rheological behavior of partially hydrolyzed oat (1-->3)(1-->4)bet a-D-glucan was compared to that of the original unhydrolyzed P-D-gluca n. Flow and oscillatory shear measurements of the nonhydrolyzed sample in aqueous solution showed behavior typical of noninteracting polysac charides, such as guar gum, in solution. The theology of partially hyd rolyzed samples shifted toward the more gel-like behavior observed wit h polymers, which tend to aggregate and form a three-dimensional macro molecular network. The aggregation may arise from a tendency of the be ta-glucan to self-associate through cellulose-like sequences in the st ructure. However, the reason why this behavior was not observed with u nhydrolyzed oat gum is not understood. It is unlikely that structural variations, such as the amount of cellulose-like sequences, accounted for the different theology, because quantitative analysis of oligosacc harides released by lichenase evidenced only minor differences between intact oat beta-glucan and hydrolyzed samples. A more likely explanat ion is that because of their lower molecular weight, the partially hyd rolyzed molecules are more mobile and diffuse more easily. Hence, they have a greater probability of forming aggregates.