Effect of pH and temperature on the hydrolysis of disodium acid pyrophosphate (SAPP) in potato processing

Disodium acid pyrophosphate (SAPP) is used in the potato industry for preventing after-cooking darkening of cooked and oil-blanched French-fried potato. SAPP-treated potatoes often develop a bitter off-flavor chemical taste due to large amounts of PO₄ absorbed from hydrolysis of SAPP solution. SAPP hydrolyzes directly to orthophosphate. Hydrolysis rate depends directly upon temperature and pH of the solution. The best control of after-cooking darkening is attained at pH 5 at 20–25°C. Increasing the concentration of SAPP solution has little effect on its stability at various temperatures and pH, and also made no great improvement on the color of the French-fry strips after par frying.