Separating the Role of Particles and the Suspending Fluid for the Flow of Soy Milks

Abstract

The paper describes a model and a simple experimental method to determine suspension transport properties, separating the role of particles from the suspending fluid. Shear stresses are described as consisting of 2 components: 1st, a shear stress caused by the flow of the suspending fluid and 2 nd , a shear stress caused by direct interaction between suspended particles. We show that the determination of these shear stresses of a complex (food) suspension is largely independent of the definition of its suspending fluid. The rheological behavior of soy milks at low and intermediate moisture contents was studied, and results are compared with those obtained previously. The method evidences that the high viscosity of soy milks is predominantly caused by direct particle interaction.

The Rheology of Colloidal and Noncolloidal Food Dispersions

“…While application of structure‐based models to rheological data does provide useful information, structure‐based analysis can provide valuable insight into the role of the structure of a dispersed system. Bodenstab and others (2003) estimated the contributions to flow shear stress of soy milk by suspended particles and the suspending fluid. where σ s is the shear stress caused by the viscous forces generated by the suspending fluid (continuous phase), and σ p is the shear stress caused by interaction between suspended particles.…”

“…The viscous contribution was estimated from the expression where the subscripts 1 and 2 refer to the values of stress and viscosity of the dispersion at temperatures 1 and 2, respectively. Typical values of temperature that were used were 10 °C and 25 °C, and 20 °C and 40 °C (Bodenstab and others 2003). Considerable care had to be used to obtain reliable samples of the continuous phase of the soy milk without solid residues, a concern with many other food dispersions such as fruit and vegetable products (Rao 1987).…”

Novel technologies for soy products, processing, and applications

“…Soymilk is a colloidal suspension containing approximately 5% protein and 10% solids (Lakshmanan et al, 2006), and suspended particle stability depends on many parameters including its composition and processing methods applied (Cruz et al, 2007;Nik et al, 2008;Ono et al, 1991). Large aggregates containing lipid, cell wall debris and proteins were identified in unheated soymilk (Bodenstab et al, 2003;Nik et al, 2008) and increased soymilk stabilities of heated and heated/homogenized soymilk were related to rupture of these large aggregates. On the other hand, Cruz et al (2007) explained increased stability of homogenized soymilk by formation of protein and fat globule aggregates.…”