Rheological and thermal studies on gelling characteristics of curdlan

Viscoelastic properties of curdlan gels and its aqueous suspensions of various concentrations were investigated by creep tests and oscillatory dynamic experiments to analyze its gelling characteristics. Temperature dependence of viscoelasticity of the curdlan gel suggested that with increasing heating temperature, interactions between curdlan molecules, forming a three-dimensional network, became stronger and the number of elastically active chains increased, which made the gel more elastic or solid-like. It also suggested that the transition temperature from thermo-reversible to irreversible gel was concentration-dependent. Increase in concentration lowered the irreversible-gel formation temperature from the generally reported 80 degrees C and decreased the amount of the thermo-reversible component in the gel. Results from both differential scanning calorimetry analyses and thermal scanning rheological measurements of curdlan supported this, suggesting that increase in concentration promoted hydrophobic interactions between the molecules at a lower temperature than at 80 degrees C, which contributed to the thermo-irreversibility of the gel. (C) 1999 Elsevier Science Ltd. All rights reserved.