Effect of sodium phosphate on the pasting, thermal, and rheological properties of potato and chickpea starches

Abstract

Differential scanning calorimetry (DSC) was used to determine the thermal properties of starch in controlled environment. Rapid visco analyser (RVA), Brookfield viscometer, and texture analyser were used to determine the effect of sodium phosphate (0.5, 1.0, and 1.5 M at pH 5, 7, and 9) on the cooking parameters, viscosity properties, and gel texture of potato (PS) and chickpea starch (CPS), respectively. Unlike chickpea starch at 0.5 and 1.0 M salt concentrations, the peak viscosity of potato starch at all salt concentrations decreased by about 50% as compared to control sample, especially at pH 5. CPS exhibited much higher setback values compared to PS. Gelatinisation temperatures of PS and CPS increased significantly (P≤0.05) as compared to control samples. Power law model confirmed pseudoplasticity of both starch gels (n<1). The DSC profile showed higher peak temperature at higher salt concentration, but lower enthalpy at higher salt concentration. Arrhenius equation showed the temperature dependency where the average activation energy (Ea = 18,629 K/J/mol) of CPS across salt concentration was higher compared to potato starch (6,094 K/J/mol). Gel hardness of the starches cooked in sodium phosphate generally increased with higher pH, except for CPS at 1.5 M sodium phosphate.