Kinetics on the turbidity change of wheat starch during its retrogradation.

Abstract

Wheat starch dispersions of 10-40% (w/w) were gelatinized and the change in turbidity of each solution during storage was measured in the 400-1100nm wavelength range. The relative transmittance, defined as the ratio of transmittance at any storage time to that at the initial time, decreased when the solutions were stored at 5 and 30°C; the decrease, reflecting the progress of retrogradation, was larger at 5°C than at 30°C. Most of the changes in relative transmission taking place over 14days were achieved during the first 90min. The change in the relative transmittance is inversely proportional to the energy required for deformation. The kinetics on change in relative transmittance can be expressed by Weibull equation. The larger rate constant at higher starch concentration could be ascribed to the state of the starch granules, which depended on starch concentration.