Phase behavior of casein micelles/exocellular polysaccharide mixtures: Experiment and theory

Dispersions of casein micelles and an exocellular polysaccharide (EPS), obt ained from Lactococcus lactis subsp. cremoris NIZO B40 EPS, show a phase se paration. The phase separation is of the colloidal gas-liquid type. We have determined a phase diagram that describes the separation of skim milk with EPS into a casein-micelle rich phase and an EPS rich phase. We compare the phase diagram with those calculated from theories developed by Vrij, and b y Lekkerkerker and co-workers, showing that the experimental phase boundary can be predicted quite well. From dynamic light scattering measurements of the self-diffusion of the casein micelles in the presence of EPS the spino dal could be located and it corresponds with the experimental phase boundar y. (C) 1999 American Institute of Physics. [S0021-9606(99)50816-7].