关键词: 木薯淀粉, 机械活化, 醋酸酯化, 淀粉醋酸酯, 取代度

Abstract: Cassava starch was mechanically activated by a stirring-type ball mill. Using acetic anhydride as esterification agent and methanesulfonic acid as catalyst, starch acetate was synthesized from cassava starch with different activation times. The effects of mechanical activation time, reaction time, reaction temperature, catalyst amount and acetic anhydride amount on esterification of cassava starch were investigated respectively by using degree of substitution (DS) of starch acetate as evaluating parameter. The results indicated that mechanical activation considerably enhanced the esterification of cassava starch, the DS increased with increasing activation time. The reasons are due to that the crystal structure and compact granule surface of cassava starch were destroyed by mechanical activation, the crystallinity decreased and reagents were easier to diffuse into starch intra-molecules. Moreover, it was also found that other affecting factors had a certain influence upon esterification and were closely related to the activation time of cassava starch, and the effects of reaction temperature, catalyst and acetic anhydride concentrations on esterification were reduced with increasing activation time. Furthermore, the structures of native starch, activated starch and high DS starch acetate were further characterized by using FT-IR.

Key words: cassava starch, mechanical activation, esterification, starch acetate, degree of substitution