Effect of pH on apparent viscosity of wholemeal oat flour water dispersions

Abstract

Research was undertaken to determine the effects of pH (1.5-12), stabilization time (1-3 h), and shear rate (200-1200 s-1) on the apparent viscosity of wholemeal oat flour-water dispersions (10% w/w). Six oat cultivars, with different content of dietary fibre, especially of (1-3) (1-4) β-D-glucans, were used in this study. The study demonstrated instability of apparent viscosity of wholemeal oat flour dispersions. An increase of viscosity was observed with the increase in stabilization time. The range of viscosity changes was related with the dispersion pH level-the greatest range of changes was noted for dispersion with pH 9.5. Wholemeal oat flour dispersions, irrespective of the pH level, displayed pseudoplastic flow behaviour. A moderate to high significant linear correlations (Pearson, p ≤ 0.05) existed between the apparent viscosity and the (1-3) (1-4) β-D-glucans, soluble dietary fibre and total dietary fibre content. Measurements of apparent viscosity of wholemeal oat flour water dispersions can be used for the estimation of particular dietary fibre fractions content, especially of (1-3) (1-4) β-D glucans. With the application of suitable measurement conditions, the content of (1→3) (1→4) β-D glucans can be explained by the apparent viscosity of the oat flour dispersion (R2 = 0.97-0.98).