Study of the phase separation behaviour of native or preheated WPI with polysaccharides

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 κ- or λ-carrageenan and pectin. Furthermore, to investigate the effect of pH on phase separation, the pH of native WPI (pH 2–12) and λ-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, ζ-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.