Protein-Polysaccharide Hydrogel Particles Formed by Biopolymer Phase Separation

Biopolymer-based hydrogel particles were fabricated using a segregation-aggregation phase separation mechanism. Pectin-coated whey protein isolate (WPI) hydrogel particles (d similar to 2 mu m) were formed when solutions of heat-denatured (90 A degrees C/10 min) WPI (1.5 %) and pectin (1.5 %) were mixed at pH 7, and then adjusted to pH 5 with constant stirring. Hydrogel particle properties and suspension appearance were strongly influenced by pH (2 to 8) and calcium chloride (0-5 mM) due to the importance of electrostatic interactions. At pH 2 to 3, extensive biopolymer complexation occurred leading to highly viscous solutions. At pH 6 to 8, biopolymer complexes disintegrated due to weakening of electrostatic attraction leading to clear solutions. Calcium addition promoted biopolymer aggregation and an increase in viscosity. All systems containing intact hydrogel particles had a whitish appearance similar to that of milk. These biopolymer-based hydrogel particles may be suitable as texture modifiers, fat replacers, or delivery systems for utilization in foods.