Abstract: An oxidized starch with the contents carboxyl groups (CCG) of 2.55% was prepared through a highly efficient oxidation method. The different oxidized parameters associated with CCG of the oxidized starch was then investigated systematically. The results indicated that the highest CCG of 2.55% can be obtained under the condition described as gelatinization temperature of 80 ℃, 1.716% FeSO₄(catalyst), 40% H₂O₂(oxidant), reaction temperature of 55 ℃ and reaction time of 1.5 h. The structures and properties of oxidized starches were characterized by FT-IR, XRD and DSC. It was found that the oxidized starch with high CCG was a polymer with amorphous phase, and different CCG gave rise to different degree of crystallization. The early gelatinization, as well as the initial oxidation of starch, took place first in the amorphous lamellae of starch. With the increase of the extent of the oxidation, the oxidation shifted to crystalline region.

Key words: oxidization, carboxyl group, oxidized starch