Shear-thickening behavior of gelatinized waxy starch dispersions promoted by the starch molecular characteristics

Abstract

An unusual shear-thickening behavior was observed in 10% w/w gelatinized waxy potato and waxy corn starch dispersions at shear rates around 20 s(-1). However, the phenomenon was not found in gelatinized dispersions of waxy rice. The aim of this study was to investigate reasons for the observed shear-thickening behavior as well as its relationship with the amylopectin molecular structure. This unique phenomenon only appears at a shear rate of about 20 s(-1) during the increasing shear rate stage of the first cycle of a two-cycle steady shear flow test. After 7 d storage, the shear-thickening behavior of waxy potato starch dispersions disappeared, while it remained in waxy corn starch dispersions. A small strain temperature sweep test applied to waxy potato starch dispersions stored for 7 d showed a significant increase in the elastic behavior of dispersions at temperatures lower than 60 degrees C. This behavior was not observed on fresh and 7 d stored waxy corn and waxy rice dispersions. The study provides valuable information on a unique rheological behavior of waxy starch dispersions and its relationship to the amylopectin structure, thus opening opportunities for the design of novel foods with desired nutritional and textural properties. (C) 2018 Elsevier B.V. All rights reserved.