The gellan sol-gel transition

The behavior of gellan during the conformational transition is discussed. This transition corresponds to the formation of a double helix from two separate coils. The influence of the counterion activity on the melting and gelling temperatures of the gels and/or the ordered conformation is also described. The sol-gel transition is studied by conductimetry in the presence of pure monovalent counterions or monovalent divalent mixtures. This method is one of the best ways of characterizing this transition. A two-step mechanism of gelation was demonstrated in the presence of monovalent counterions. In the presence of divalent counterions, at a given ionic strength, the mechanism of gelation and the gel properties depend only on the ratio Y between divalent and monovalent counterions. Three types of gel behavior are described as a function of Y and ionic strength. Copyright (C) 1996 Elsevier Science Ltd