Aqueous solutions of globular proteins (beta -lactoglobulin) at pH 7 and 0.1 M NaCl were heated in the presence of various concentrations of polysaccharide (kappa -carrageenan). The fraction of unaggregated proteins was determined as a function of heating time with size exclusion chromatography. The rate at which the proteins aggregate is independent of the polysaccharide concentration at least up to 9 g/L kappa -carrageenan. The protein aggregates were characterized using light scattering. At modest concentrations (up to 1 g/L) the presence of kappa -carrageenan accelerates the growth of the aggregates and therefore the gel formation, but the structure of the aggregates is not modified. At higher concentrations kappa -carrageenan induces phase separation of protein aggregates.