Role of starch granule characteristics (volume fraction, rigidity, and fractal dimension) on rheology of starch dispersions with and without amylose

The link between rheological behavior and morphological-structural characteristics of gelatinized starch granules has been studied in two starch dispersions (SDs): a cross-linked waxy maize (CLWM), and tapioca starch, a tuber starch with 19.3% amylose. Based on the power law relationship between the elastic modulus and volume fraction of the granules predicted by scaling theory, fractal dimension values were obtained for CLWM starch D = 2.81, and tapioca starch D = 2.79, suggesting that both starch granules have highly convoluted surfaces. However, the preexponential coefficient (G(theta=1)(')) for CLWM SDs was an order of magnitude greater than that for tapioca SDs, in the same range of volume fractions. The G'(theta=1) was mainly dependent on the granule rigidity, and the amylose content in the continuous phase played only a minor role in the rheological behavior.