Characterization of waxy starches phosphorylated using phytic acid

Waxy maize and waxy rice starches were subjected to dry heating in the presence of phytic acid at 120 °C for 6 or 24 h under alkaline conditions to induce phosphorylation. Dry heating at 120 °C for 24 h with phytic acid increased the residual phosphorus content of waxy maize and waxy rice starches from 11.5 to 92.9 ppm and from 27.5 to 79.3 ppm, respectively. 31P Nuclear magnetic resonance (NMR) analysis revealed the presence of monostarch monophosphate in the treated starches. The pasting viscosity of the starches was substantially changed by the phosphorylation, showing increases in peak viscosity, breakdown, and setback viscosity, but decrease in pasting temperature. Paste clarity and swelling power also increased after phosphorylation. Reduced melting temperature and enthalpy were observed for the phosphorylated starches. Thus, phytic acid is an effective reagent for phosphorylating starch to improve its pasting properties.