Rheaological behavior of high acyl gellan gum solution at gel point

The sol–gel transition temperatures of high acyl gellan gum solution were investigated using rheaological measurements. The sol–gel transition temperatures were determined from three criteria: the crossover of storage modulus G′ and loss modulus G″, the linear extrapolation method, and the Winter's criterion. The results showed that the Winter's criterion was more suitable to determine the sol–gel transition temperature. The sol–gel transition temperature increased with the increasing gellan concentration. The relaxation critical exponent n can be determined by the Winter's criterion. There is no universal n for the gelation in high acyl gellan gum solutions, indicating that this gelation belongs to the cross-linking of existing macromolecules. The values of n decreased with increasing concentration of gellan gum solution. The fractal dimension df calculated from n without the screened hydrodynamic interaction nor the excluded volume effect suggested a denser structure in the critical gel with higher c. The gelation enthalpy (ΔHgel) was calculated by Eldridge–Ferry model.