Characterisation and modelling of time-independent and time-dependent flow behaviour of sodium alginate dispersions

Abstract

The time-independent and time-dependent rheological behaviour of sodium alginate dispersions were determined. The concentration of sodium alginate in the dispersions and temperature of measurement were between 1% and 3%, and 25 and 55 °C, respectively. Shear-thinning behaviour was observed for these alginate dispersions when subjected to progressively increasing shear stresses. The Cross power indices (m) were between 0.57 and 0.82. The time-dependent studies were conducted by loop experiments at constant shear rates of 25, 125 and 625 s-1. The thixotropic loop and the different time-dependent parameters were sensitive to the concentration of alginate and temperature of measurement. The models of Weltman, Mangelsdorf and the three-parameter non-linear model were suitable to predict the shear stresses at constant shear rates, as judged by root mean square error values. The coefficient of thixotropic breakdown with shearing (M) could be obtained from forward curve while it gave an indication of structural build-up when shear rate was progressively decreased. © 2009 Institute of Food Science and Technology.