Selected physicochemical properties of rice flour, modified tapioca starch, and their mixtures after a limewater soaking treatment

Abstract

Effects of a saturated limewater soaking treatment on physicochemical properties of Khao Dawk Mali 105 rice flour (KDML105), rice flour, modified tapioca starch (MTS), and their mixtures were investigated. The limewater soaking treatment caused some birefringence losses of flour granules and a significant (P ≤ 0.05) increase in pH and flour solubility. All flours and flour/starch mixtures soaked in limewater exhibited lower onset and peak temperatures and reduced gelatinisation enthalpy by DSC in relation to peak viscosity, final viscosity, and setback, when compared to unsoaked flours. MTS had the highest peak viscosity and breakdown followed by KDML105 and rice flour, respectively, regardless of the limewater soaking treatment. The gel obtained from limewater-soaked KDML105 had the lowest firmness and a low gel retrogradation. After limewater soaking, both mixtures (KDML105:rice flour:MTS, 1.4:0.6:1 and 1:1:1) containing different amounts of KDML105 and rice flours gave a soft and sticky gel. This study demonstrated that chemical modification by a limewater soaking treatment induced some changes in properties of rice flour, MTS, and their mixtures.