Predicting the rheology of food biopolymers using constitutive models

Abstract

Several constitutive models have been discussed to explain data for some foods in diluted and concentrated systems. Firstly, the theories of Rouse and Zimm, as well as rod-like theory, were used to study the conformation of the pectins in dilute solution. Among the dilute theories, the random coil theory of Zimm best explained the experimental data and suggested a certain level of intermolecular interaction present in the dilute pectin solution. The Bird-Carreau constitutive theory with four empirical constants and zero shear limiting viscosity was used to describe the viscoelastic properties of the solutions of the guar, CMC/guar, glutenin, gluten and wheat flour doughs. The Bird-Carreau model was able to predict η and η′ in the high and low frequency regions for 1% guar solution. In the case of CMC/guar blend, the Bird-Carreau model explained steady shear and dynamic properties very well in the higher shear rate or frequency region of 1–100 s −1. However, η″/ω does not tend to a zero shear constant value. The Bird-Carreau model also gave good predictions on the rheological properties of gluten and glutenin biopolymers in the free-flow region. The polydisperse type, Doi-Edwards model, fits the experimental G′ and G″ better than the monodisperse model for 5% apple pectin dispersion. However, there is still a discrepancy between experimental and predicted values.