抄録
The flow behavior and dynamic viscoelasticity of deacetylated gellan gum solutions were measured with a rheogoniometer. The gellan gum showed Newtonian behavior with a range of concentration below 0.9%, but plastic flow behavior above 1.0% at 25°C. A gelation occurred in polysaccharide 6concentrations over 0.8% upon cooling, and a melting temperature was observed at 15 and 20°C at 0.8 and 1.0% concentrations, respectively. In the presence of CaCl2 (6.8 HIM), the dynamic modulus of gellan gum showed a very high value at low temperature at the concentration of 0.2%, and increased with increasing temperature up to 80°C, which was estimated to be a melting temperature, then it decreased. Howevei>the gellan showed a little increase of dynamic modulus even at the concentration of 0.4% in the presence of NaCl (16.6 mM) or KC1 (13.5 mM). Gelation occurred for gellan gum in acid and alkaline range after reaching a pH 2.6 and 11.2 by addition of 100 mM HCl and Ca(OH)2. The rheological characteristics of the gellan gum molecules might be essentially attributed to intra- and inter-molecular associations, possible structures of which have been proposed.
