Rheological behavior of Aeromonas gum in aqueous solutions

Rheological properties of Aeromonas (A) gum in pure water in the range from dilute to concentrated solution were examined using the Rheometric Scientific ARES controlled strain rheometer. It demonstrated typical polyelectrolyte behavior in solution, yielding intrinsic viscosity of [eta] = 4850 mL/g. As found for normal disordered polysaccharides, shear-thinning behavior was also observed. The zero shear viscosity (eta(0)) and specific viscosity (eta(sp)) increased with an increase of the polysaccharide concentration (c) and degree of space-occupancy (c[eta]), respectively, similar to the general trend of most disordered polysaccharides. The critical concentration c*, at which the transition from a dilute solution of independently moving chains to an entangled network occurred, was determined to be ca. 1% from steady and dynamic experiments of the A gum solutions. The results from dynamic experiments revealed that the behavior of all the solutions was characteristic of polymer solutions without any evidence of gel-like character. The values of shear storage modulus (G') were found to vary with c(4). The higher exponent (4) may be contributed to an increase of continuous networks as a result of the entanglements when the polymer concentration increased. The complex viscosity and steady shear viscosity deviated from the Cox-Merz rule, owing to the formation of aggregates. (c) 2005 Elsevier Ltd. All rights reserved.