Interactions between carrageenans and casein micelles: electrophoretic and hydrodynamic properties of the particles

Complexes of casein micelles with lambda-, iota- and kappa-carrageenans have been made in solutions containing milk diluted 100-fold and concentrations of up to 0.2 mg/ml of the polysaccharides. The electrophoretic mobilities and diffusion coefficients of the complexes were measured, with some studies of the molecular weights. The results are consistent with binding of carrageenan to the casein micelles until the surfaces of the micelles were saturated, after which some further aggregation of the complexes could occur. Conform ationally ordered (helical) iota-carrageenan and conformationally disordered ('random coil') lambda-carrageenan both showed similar aggregation behaviour. kappa-Carrageenan, by contrast, gave no evidence of micellar aggregation when present as a random coil, but on conversion to the helical form (by addition of K(+)) it caused precipitation of casein micelles under all conditions studied.