Abstract: The acetyl groups are attached to konjac glucomannan (KGM), deacetyltion occurs on alkaline treatment and causes the association of molecular chains. The improved method of konjac glucomannan (KGM) carboxy methylation was proposed in this paper according to the effects of deacetylation. Carboxymethyl KGM (CMK) were synthesized by blending KGM with etherification agent first and then basifying and catalyzing in ethanol. Basifying first and then etherifying prepared traditional carboxymethyl KGM (TCMK). Using both degree of substitution (DS) and apparent viscosity (η) as evaluation indexes, the reaction conditions were determined. The contrast of two modification methods show different sequence of deacetyltion and the results indicate that the CMK has better value of DS=0.5278 (70℃, pH 12 for 3 hours) and η=15.57 Pa·s (55℃, pH 9 for 2 hours) and excellent hydrated rate. The structure of products was characterized by means of infrared spectra, wide-angle X-ray diffraction and differential scanning caloriimetry and the effect of deacetylation in course of konjac glucomannan carboxy methylation was analyzed.

Key words: Konjac glucomannan, Deacetylation, Carboxy methylation, Structure characterization