Prediction of the nonlinear transient and oscillatory rheological behavior of flour suspensions using a strain-separable integral constitutive equation

The evaluation and development of validated models for the nonlinear viscoelastic (VE) behavior of materials is an important area of research, which has impact on a number of industrial processes including those in the food industry. Various nonlinear VE models have been developed over the years and evaluated for petroleum-based polymers; however, our understanding of the nonlinear VE behavior of biopolymers of industrial import lags our understanding of synthetic polymers. In the work reported herein, the nonlinear VE behaviors of defatted oat flour, oat bran, barley flour, and oat flour suspensions were investigated. The rheological properties were measured using a Rheometrics Series IV controlled-strain rheometer equipped with a cone and plate fixture. The measurements were conducted at 23±0.5°C. The rheological data were interpreted using a strain-separable K-BKZ type (Wagner) model with a damping function evaluated from stress relaxation data. The Wagner model was found to provide an accurate description of the rheological behavior of the suspensions produced from defatted oat flour, barley flour, and oat bran. For suspensions produced from oat flour, the model predictions deviated from the experimental data to a greater degree than the other materials.