Cold gelation of 4-O-methyl-D-glucurono-D-xylan in aqueous media: influence of salts on the rheological behaviour.

The rheological characterization of semi-dilute aqueous solutions of 4-O-methyl-D-glucurono-D-xylan (MGX), extracted from beech wood sawdust, has evidenced a reversible cold gelation displaying a large hysteresis. As an example, for a 180 g/L MGX solution in pure water, a G"/G' crossing at 16.6 °C upon cooling has been found, leading to a gelation, and a G'/G" crossing at 38.3 °C upon heating back to the initial temperature of 50 °C, leading to a dissociation of the gel state. In this study, we demonstrate that such thermal transitions can be modulated with the MGX concentration (from 150 to 190 g/L), respectively from 11.3 to 19 °C for the cooling transition and from 30.8 to 40.5 °C for the heating transition. Gelation is also favoured with the addition of monovalent salts like LiCl, NaCl, and KCl, and more particularly with divalent salts like MgCl2 and CaCl2, at the same ionic strength (0.15 M). The observed increase of MGX structuration at 10 °C in the presence of salts (notably with CaCl2), and the subsequent retention of a gel state at body temperature could be useful for biomedical applications.