SYNTHESIS AND PROPERTIES OF STARCH PHOSPHATE MONOESTERS

Starch phosphates were prepared with a view of dependence of their characteristics on factors affecting their synthesis. Factors examined include concentrations of urea and phosphoric acid, reaction time and temperature and PH of the reaction medium whereas the properties embrace acidity, nitrogen content, viscosity, swellability and solubility. Results indicated that incorporation of urea in the reaction mixture (starch, phosphoric acid and sodium pyrophosphate) varianty alters the acidity but with the certainty that the value of the acidity still far behind that obtained in absence of urea. On the other hand increasing the phosphoric acid concentration brings about a substantial increment in both acidity and nitrogen content. Both acidity and nitrogen content increase also by raising the temperature from 110 to 150-degrees-C, and by increasing the reaction time from 0.5 to 1.5 h. Highest acidity and nitrogen content are obtained at the lowest pH; increasing the pH causes a sharp decrement in the acidity and nitrogen content. Furthermore, the results indicate that viscosity, swellability and solubility, properties of the so obtained modified starches rely largely on factors controlling the condition of the treatment. The latter yields various esterified starches such as starch phosphate, starch ammonium phosphate, starch carbamate and crosslinked starch. The magnitude of each of these esters in the reaction products in turn, determine the said properties.