ON THE EXISTENCE OF 2 DIFFERENT SECONDARY STRUCTURES FOR THE XANTHAN IN AQUEOUS-SOLUTIONS

The increase of the viscosity reported when native xanthan broth is heated, before isolation, suggests the existence of two different secondary molecular structures showing different hydrodynamic behavior. In this paper, experiments are described which support this hypothesis. It is possible that these secondary structures correspond to some of those recently predicted by D. Gagnaire et al. It is also demonstrated that the relative stability of the two secondary structures can be controlled by the experimental conditions. In addition, it is shown that the conformation which exists at the time of precipitation is maintained when the polymer is redissolved in a solvent in which the conformational melting temperature T//M is higher than the dissolution temperature.