PHASE-SEPARATION IN DEXTRAN LOCUST BEAN GUM MIXTURES

Dextran/locust bean gum (LEG) mixtures have been prepared and investig ated with respect to their phase separation behaviour. These systems e xhibited phase separation at 20 degrees C, the upper phase, itself bip hasic, 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 m eans of rheological dynamic measurements. Clearly, its behaviour was t ypical of a gel, the three-dimensional structure of which can be ascri bed to self-association of LEG chains owing to the very high concentra tion of the galactomannan in this upper phase. The self-association of the galactomannan was confirmed by fluorescence microscopy carried ou t on mixtures containing fluorescein isothiocyanate (FITC)-labelled de xtran. The rheological behaviour of a concentrated LEG solution was al so investigated as a function of time, clearly showing progressive for mation of a weak gel structure. Copyright (C) 1996 Elsevier Science Lt d