Micro-heterogeneity and micro-rheological properties of high-viscosity oat β-glucan solutions

Soluble fibre β-glucan is one of the key dietary materials in the healthy food products known for reducing serum cholesterol levels. The micro-structural heterogeneity and micro-rheology of high-viscosity oat β-glucan solutions were investigated by monitoring the thermally driven displacements of well-dispersed microspheres via video fluorescence microscopy. By comparing the distribution of the time-dependent mean-square displacement (MSD) and ensemble-averaged MSD of polystyrene microspheres imbedded in four concentrations of β-glucan solutions, we found that the solutions exhibited perfectly homogeneous behaviour at ⩽1%, but showed a certain degree of heterogeneity at 2%. Micro-rheology investigation revealed that β-glucan solutions displayed nearly perfect viscous behaviour at ⩽1%, but the property changed into viscoelastic at 2%. Both micro-structural heterogeneity and micro-rheological property shifts occurred over a small concentration range, between 1% and 2%, of β-glucan.