Phytate-mediated phosphorylation of maize, rice, and potato starches at different pH conditions

Maize, rice, and potato starches were dispersed with phytate at pH 7, 9, and 11, and were subjected to dry-heating at 130 °C for 12 h. The residual phosphorus content and structural characteristics revealed that the treatment resulted in starch phosphorylation. Further, pasting viscosity, clarity, solubility, and swelling power were analyzed to determine the physicochemical properties of the phosphorylated starch. These heat-treated starches retained phosphorus mainly in the form of monostarch monophosphate. Phosphorylation increased the peak viscosity and decreased the pasting temperature in maize and rice starches, but not in potato starch. Paste clarity, solubility, and swelling power were also increased in phosphorylated maize and rice starches. Phosphorus content, paste clarity, solubility, and swelling power were the highest at pH 7, but the maximum paste viscosity was at pH 9. These results indicate that phytate can be used for starch phosphorylation, with the reaction efficiency based on the botanical source of the starch and the reaction pH.