Preparation and rheological characterization of carboxymethyl konjac glucomannan

Konjac glucomannan (KGM) was subjected to chemical modification via carboxymethylation under a variety of conditions and their physico-chemical properties were investigated. It was found that the extent of carboxymethylation, expressed as degree of substitution (DS) value, increased with increasing concentration of the etherifying agents. The DS value was affected largely by the amount of sodium hydroxide. Carboxymethylated KGM pastes were characterized by use of dynamic viscoelasticity measurements. Both storage modulus G′ and loss modulus G″ of carboxymethylated KGM pastes decreased and became more frequency dependent with increasing DS value at a constant proportion. Viscoelasticity of carboxymethylated KGM was negligibly affected by the addition of salts, i.e. NaCl, CaCl2, KCl, regardless of the DS value. Thus, the introduction of carboxymethyl group in KGM molecules suppresses a mutual interaction of KGM, i.e. intermolecular hydrogen bond, and tended to a more liquid like rheological behavior.