Phase and Rheological Behavior of High-Concentration Colloidal Hard-Sphere and Protein Dispersions

Abstract

Colloidal hard-sphere particles of narrow-size distribution exhibit crystalline and glassy states beginning at the particle volume fractions φ=0.494 and φG=0.58, respectively. Dynamic rheological data on the dispersions was strongly modified to solid-like behavior as φ approached φG. In addition, cooperative motion in structural relaxation has been observed microscopically in the colloidal dispersions near the glassy state. Very high viscosities and glassy states were also found in high-concentration dispersions of sodium caseinate, and the globular proteins: bovine serum albumin and β-lactoglobulin. Viscosity models developed for hard-sphere dispersions provided reasonable predictions of relative viscosities of colloidal protein dispersions. Dispersions of food colloidal particles may be employed in studies, in which volume fraction is the thermodynamic variable, for understanding the relaxation and transport processes related to first-order and colloidal glass transitions