In situ pH-decrease-induced gelation of sodium alginate/carboxymethylated konjac glucomannan

摘要

The gelation kinetics and rheological properties of a mixture system containing two anionic polysaccharides, sodium alginate and carboxymethylated konjac glucomannan, in the presence of glucono-delta-lactone were investigated with dynamic viscoelastic measurements. The slow release of protons induced by glucono-delta-lactone gave birth to partly uncharged polymer chains and partly shielded electrostatic repulsion, resulting in an interpolymer association. This segregative interaction brought about a significant improvement in the elastic modulus of the resultant gel. The strongest synergism occurred at a carboxymethylated konjac glucomannan concentration of 29.9 wt %, exhibiting the highest gel strength. Increasing the content or the degree of substitution of carboxymethylated konjac glucomannan resulted in slower gelation kinetics. The fractal dimension of the incipient gel, which was not greatly affected by the mixing ratio or the degree of substitution of carboxymethylated konjac glucomannan, reflected a rather compact gel structure network. (C) 2008 Wiley Periodicals, Inc.