Rheological behaviour of heated potato starch dispersions

The study was designed to investigate the theological properties of heated potato starch dispersions. Water suspensions of starch were heated at 65, 80 or 95 degrees C for 5, 15, 30 or 60 min. The dispersions obtained were examined for granule size distribution and rheology. It was found that the starch dispersions significantly differed in both respects. The mean diameters of starch granules were largest for the dispersion heated at 65 degrees C and smallest for that heated at 95 degrees C. As the heating temperature was raised, the yield stresses and consistency coefficients decreased, while the flow behaviour indexes and Casson plastic viscosities increased. There were also differences in the viscoelastic properties of the dispersions: for those heated at 65 degrees C the storage and loss moduli increased with heating time whereas for those heated at 80 degrees C both moduli decreased.