Rheological properties of starches from grain amaranth and their relationship to starch structure

Amaranth starch (Amaranthus cruentus L. and Amaranthus hypochondriacus L.) in this investigation possessed a relatively small and uniform granule size of a type A pattern obtained by X-ray diffraction, with the degree of crystallinity ranging from 24.5 to 27.9%. This was followed by work on steady and dynamic rheological properties on shear of seven native amaranth starches. Aqueous pastes (5% solids) exhibited shear-thinning behavior, and the flow behavior was fitted with the Herschel-Bulkley equation (regression coefficients were over 0.99). Cultivar V69 showed much higher G' (storage modulus) and G '' (loss modulus) than the other samples and produced a solid-like gel, which could be attributed to the high amylose content of its network. Correlation analysis revealed that amylose content was positively correlated with G' and negatively with the loss tangent (tan delta) of the material.