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 (ΔH). 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.