EFFECT OF SOLUBLE SUGARS ON GELATINIZATION AND RETROGRADATION OF SWEET-POTATO STARCH

The effect of water-soluble sugars contained in sweet potato on gelatinization and retrogradation of starch was studied by means of differential scanning calorimetry. Gelatinization peak temperature T(p) and gelatinization enthalpy increased with increasing sugar concentration. The shift of T(p) to higher temperatures was attributed to the stabilization of the crystalline region in starch and the immobilization of water by sugar molecules. The effect is larger in the order sucrose, glucose, fructose. All these sugars prevent retrogradation of sweet potato starch paste, and the order of effectiveness is the same as in the case of increase in gelatinization temperature. The effect of sucrose concentration on T(p) was explained by a zipper model approach.