Abstract
The non-Newtonian behavior and dynamic viscoelasticity in aqueous solution of potato amylopectin were measured with a rheogoniometer, and the molecular origin for the rheological characteristics were discussed in comparison with those of rice amylopectin. The flow curves, at 25t, of potato amylopectin showed shear-thinning behavior at 2.0 and 4.0% concentration, but plastic behavior at 6.0%, the yield value of which was estimated to be 0.8 Pa. Although the dynamic viscoelasticity of rice amylopectin showed a constant value, it decreased in potato amylopectin solution when the temperature was increased. The tan s value was 1.15 at a concentration of 6.0% even at 0°C. The dynamic modulus decreased with the addition of urea (4.0 M) and in alkaline solution (0.05 N and 0.10 N NaOH) during an increase in the temperature. An increase of the dynamic modulus, however, was observed in 85% DMSO. A slight intramolecular association in potato amylopectin molecules seems to beinvolved in aqueous solution. The phosphate groups attached at C-6 seem to prevent intramolecular associations of potato amylopectin molecules in aqueous solution.
