Effect of salt addition on gelatinization and rheological properties of sweet potato starch–xanthan gum mixture

The effect of NaCl at different concentrations (1.0–5.0%) on the gelatinization and rheological properties of sweet potato starch (SPS)–xanthan gum (XG) mixtures was examined. Steady shear rheological properties of SPS–XG–NaCl mixtures were determined from the rheological parameters for the power law and Casson flow models. The consistency index ( K ), apparent viscosity ( η a,100 ,), and Casson yield stress ( σ oc ) values of SPS–XG–NaCl mixtures were much lower than those of the control (0% NaCl) and also decreased with an increase in the NaCl concentration. The storage modulus ( G ′) values of SPS–XG–NaCl mixtures were much higher than the loss modulus ( G ″), indicating that the addition of NaCl influences the synergistic effect in the elastic properties of XG in the SPS–XG–NaCl mixture systems. The addition of NaCl resulted in a significant increase in the peak, breakdown, final, and setback viscosities, and pasting temperature of SPS–XG mixture. In general, differential scanning calorimeter (DSC) studies conveyed that the presence of NaCl resulted in an increase in the gelatinization temperatures ( T o , T p , and T c ) and a decrease in gelatinization enthalpy (Δ H ). In general, these results suggest that the addition of the NaCl to SPS–XG mixtures modified the pasting, rheological, and thermal properties, depending on the NaCl concentration.