Rheological behaviour of sage (Metroxylon sagu) starch paste

Rheological behaviour of gelatinized sage starch solution was studied over the shear rate range of 13.61-704 s(-1) at various concentration and temperature ranges. A power law equation was used to describe the rheological behaviour of the starch solution, while the effect of temperature was evaluated by the Arrhenius equation. The effect of starch concentration on apparent viscosity was studied using the exponential model describing the relationship between apparent viscosity and concentration. Consistency index (kappa) increased with concentration and decreased with the increase of temperature. Flow behaviour indices (eta) were within the range of 0.495-0.559 which indicated the pseudoplastic nature of gelatinized sage starch. The amount of starch and shear rate affect activation energy (Delta E). Depending on the shear rate and concentration, activation energy varied from 0.619 to 1.756 kcal mol(-1). A mathematical relationship correlating the various parameters (temperature, concentrations, shear rates) was tested for its significance and validity. (C) 1999 Elsevier Science Ltd. All rights reserved.