The purpose of this study was to prepare and characterise biopolymer phase separation based on the heated or non-heated whey protein isolates and various polysaccharides complexes. Initially, non-heated or preheated whey protein isolates (1-5% (w/v)) were mixed with 0-3% (w/v) of kappa- or lambda-carrageenan and pectin. Furthermore, to investigate the effect of pH on phase separation, the pH of native WPI (pH 2-12) and lambda-carrageenan (pH 2-9) were varied and combined to obtain a phase diagram. Biopolymer complexes obtained from two phase-separated zones were characterised in terms of their particle size, zeta-potential and morphology. Regarding the denatured whey protein isolates with polysaccharides mixtures, a segregative phase separation occurred due to the partial alteration of the protein structure from the globule form to the filament form, thus altering the hydrophobic cross-links and generating water-in-water emulsions with polysaccharides. However, the non-heated whey protein isolates formed the aggregated complexes through precipitation with polysaccharides at certain mixing ratios. (C) 2014 Elsevier Ltd. All rights reserved.