- Materials Science; Hydrocolloids; Flow behaviour; Flow parameters; Intrinsic viscosity; Kraemer constant
The aim of this study was to characterize rheological properties of shear-thinning ! polysaccharides (guar gum, κ-carrageenan, xanthan gum), which are widely used as food hydrocolloids in food processing. Viscometric analysis of the polysaccharides solutions both in distilled water and in 0.07M KCl at the temperature range of 20 to 45°C confirmed strong concentration dependency of the solutions viscosities as reflected in observed significant changes of the flow parameters, calculated by the Ostwald-de Waele and Herschel-Bulkley rheological models. The consistency coefficient (k) of the solutions increased with concentration, whereas the flow behaviour index (n) decreased in all studied hydrocolloids except xanthan gum aqueous solutions. The temperature had an opposite effect in comparison to one obtained for concentration dependencies; k decreased with temperature, while n increased. However, xanthan gum both in water and KCl exhibited a different patterns of the flow parameters dependencies on temperature, and provided some specific properties, such as relatively viscous solutions at higher temperatures, and a noticeable yield stress in the whole studied temperature range. The transition from double helical structure of the polysaccharides to single coil conformation in water and KCl aqueous solutions at 30 °C temperature was proved by the steep change of the Kraemer constant temperature dependence.