Effect of metal ions on physicochemical and rheological properties of octenyl succinate starches

•Octenyl succinate starch is a good carrier of Ca, K and Mg ions.•Potassium ions increased solubility and water-binding capacity of OSA starches.•Magnesium ions decreased hydrodynamic volume of starch molecule in solution.•Metal ions increased rheological stability of starch pastes during heating and cooling.•OSA starches substituted with Mg and Ca ions were less resistant to shear forces.

The objective of this study was to determine the effect of substituting octenyl succinate potato starches with magnesium, calcium and potassium ions on their physicochemical and rheological properties. Materials used for the study were potato starches esterified with using 30 mL/kg or 90 mL/kg of octenyl succinic anhydride (OSA) and afterwards substituted with metal ions. The effectiveness of the esterification process and contents of magnesium, calcium, and potassium were determined in the study. All starch samples were analysed for: molecular weight distribution, water binding capacity and solubility in water. Pasting properties, intrinsic viscosity and flow curves were studied as well. The results indicated that the apparent number-average (Mn) and weight-average (Mw) molecular weights as well as intrinsic viscosity of OSA starches decreased, with the greatest effect observed for the substitution with magnesium ions. The OSA starches substituted with potassium ions showed the highest solubility in water. In turn, the presence of magnesium ions in the starches esterified with 30 mL/kg of OSA resulted in a decrease in all viscosity values and also in values of shear stress within the shear rate range. Out of the starches esterified with 90 mL/kg of OSA such changes were observed upon substitution with calcium ions.