The effect of annealing under acid or alkaline environment on the physicochemical and functional properties of wheat starch

Abstract

The annealing of wheat starch was performed in dilute acid and alkaline media at 40 °C and 45 °C. To highlight the effect of these processes on wheat starch, the scanning electron microscopy and the optic microscopy under normal and polarized light, the Wide-Angle X-ray Scattering patterns and the colour parameters were analysed without revealing significant changes in comparison to the native wheat starch and samples submitted to the classical annealing process in pure water. Most striking changes induced were observed upon additional hydrothermal treatment above wheat starch gelatinization temperatures and when analysing the water-binding capacity and the solubility, the starch granules swelling kinetics, the pasting behaviour of starch-water dispersion as well as the flow properties of gels recovered. It is likely that the complementary changes induced by these variants of annealing are meanly related to the restructuration of the amorphous phase inside granules that modify irreversibly their swelling capacity as well as their susceptibility to collapse upon further hydrothermal treatments. Although the magnitude of the changes induced by these processes seems to depend on the incubation temperature, the same trends were observed when compared the results from the two incubation temperatures applied. Coupling the annealing process with incubation in diluted acid or alkaline media can be used as effective way to expand the possibilities of using wheat starches in various industries.