Phase separation, rheology and structure of micellar casein-galactomannan mixtures

The properties of micellar casein-galactomannan (guar gum and locust bean gum) mixed systems have been investigated at 20 degrees C, pH 7 and in 0.25 M NaCl: in these conditions, the mixtures tended to phase separate probably due to depletion-flocculation mechanisms. The ternary phase diagram has been established for each galactomannan-casein system according to the biopolymer concentrations. The rheological properties of these mixed systems have been investigated in the monophasic domain, as well as in the biphasic one, Modifications of the flow and the viscoelastic properties were clearly evidenced in the two-phase domain. The ultrastructure of the galactomannan-micellar casein mixtures has been described using confocal laser scanning microscopy. In the biphasic domain, observations of the mixed system at concentrations corresponding to those of rheological measurements clearly evidenced that the phase separation process has yielded a continuous network mostly composed of the aggregated micellar casein. (C) 1999 Elsevier Science Ltd. All rights reserved.