Expansion, Color and Shear Strength Properties of Com Starches Extrusion‐Cooked with Urea and Salts

Abstract

AbstractSodium chloride, sodium bicarbonate and urea were mixed with normal corn starch (25% amylose) and extrusion‐cooked at 140°C. The expansion ratio of the starch increased from 13 to 16.9 as the sodium chloride concentration was increased from 0 to 1 g per 100 g of starch (d. b.) and then decreased. As the concentrations of sodium bicarbonate and urea in the starch mixtures were increased, the expansion ratios decreased gradually from 13 to 11.9 and 8, respectively. Starch‐sodium bicarbonate mixture extrudates were brownish‐yellow in color. In a follow‐up study, corn starches with amylose contents of 0, 25, 50 and 70% were extrusion‐cooked with the above chemicals added at a level of 1 g per 100g starch. In general, the addition of sodium chloride increased the expansion ratio of all starch extrudates by 0.5 to 5.5 units, whereas sodium bicarbonate and urea decreased expansion by 1 to 6 units. The overall color of the starch extrudates, prepared with and without sodium bicarbonate, tended towards brownish‐yellow with increasing amylose content.