Phase separation in dextran locust bean gum mixtures

Dextran/locust bean gum (LEG) mixtures have been prepared and investigated with respect to their phase separation behaviour. These systems exhibited phase separation at 20 degrees C, the upper phase, itself biphasic, being enriched with locust bean gum but also containing dextran, whereas the lower phase contained only dextran. This lower phase was a liquid. The upper phase, which did not flow, was characterized by means of rheological dynamic measurements. Clearly, its behaviour was typical of a gel, the three-dimensional structure of which can be ascribed to self-association of LEG chains owing to the very high concentration of the galactomannan in this upper phase. The self-association of the galactomannan was confirmed by fluorescence microscopy carried out on mixtures containing fluorescein isothiocyanate (FITC)-labelled dextran. The rheological behaviour of a concentrated LEG solution was also investigated as a function of time, clearly showing progressive formation of a weak gel structure. Copyright (C) 1996 Elsevier Science Ltd