Rheaological behavior of high acyl gellan gum solution at gel point

ABSTRACT

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 d_f 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 (ΔH_gel) was calculated by Eldridge–Ferry model.

KEYWORDS:

• High acyl
• Gellan gum
• Sol–gel transition
• Gel
• Rheaological measurements

Additional information

Funding

This work was supported by the National Natural Science Foundation of China: [Grant Number 51103131], Food Science and Engineering the most important discipline of Zhejiang province: [Grant Number JYTSP20142091], and MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Zhejiang University: [Grant Number 2015MSF002].