Shear-induced aggregate formation in starch solutions

Shear-thickening behavior and shear-induced pattern formation have been observed in semidilute starch solutions. While the shear-thickening behavior is due to breaking up of highly concentrated gel-like structures dispersed in dilute starch solutions, the pattern-forming behavior is not well understood. The pattern formation, observed when the starch solution is exposed to a high shear field, is a consequence of shear-induced aggregation and is not related to shear-thickening behavior. The patterns have been observed above a certain critical threshold shear rate regardless of the starch type. s report, it is shown that the product of shear time and fourth power of shear rate is a controlling factor for the formation of shear-induced aggregates in starch solutions. Since starch solutions prepared under harsh conditions did not show shear-induced aggregate formation, it is suggested that the aggregates are formed from incompletely solubilized starch residues in its apparent solution.