Determination of Dynamic Moduli of Soy Doughs Using an Orthogonal Rheometer1

Abstract

The orthogonal rheometer in principle provides a relatively simple means of applying a dynamic strain to polymers to determine the dynamic storage and loss moduli (G′, G″) as functions of frequency and strain. In applying this technique to soy doughs, surface evaporation of water from the samples was found to be a serious problem, but when evaporation was controlled, good reproducibility for G′ and G″, was obtained. The moduli were very sensitive to dough moisture level, with G’ changing by a factor of 10 over the moisture range 40 to 50%. Plate diameter and percent strain both affected the absolute values of G′ and G″, though the effects were relatively small. Log G′ and log G″ increased linearly with decreasing nitrogen solubility index. The two major advantages of the orthogonal rheometer for such food systems are the ease of operation and the fact that sample thickness can be chosen to obviate problems associated with sample heterogeneity. Nevertheless, the effects of plate diameter and percent strain need more extensive study.

Effects of Mixing Soybean Flour Doughs on Their Dynamic Moduli Measured in an Orthogonal Rheometer

“…Figure 2 shows the effect of dough moisture content on the logarithm of the moduli. The moduli increased dramatically with decreasing moisture, confirming results from a previous study (Jasberg et al 1981). Data from 1 min of handmixing are included for comparison.…”

“…4). In a previous study (Jasberg et al 1981) there was a slight decrease in moduli with strains of up to l%%. In this experiment, only strains of 2% or more caused moduli to decrease with a much smaller decrease in G" than G'.…”

“…The orthogonal rheometer (eccentric rotating disks) has been used to study soybean dough (prepared from defatted soy flour) rheology (Jasberg et al 1981). However, the mixing method used to prepare samples needed to be improved.…”

Analysis of the complex rheological properties of highly concentrated proteins with a closed cavity rheometer

“…More recently, analysis was carried out in the non-linear range [29,30], which is more relevant to processes where high deformations take place. Besides bread and gluten doughs, conventional rotatory rheometers have also been used for predicting the rheological behavior of soy-based dough (either soy flours or soy protein isolates) in extrusion processing [31][32][33].…”