Complexation of pea protein isolate with dextran sulphate and interfacial adsorption behaviour and O/W emulsion stability at acidic conditions

Summary This study was aimed at improving the emulsifying property and physical stability of pea protein isolate (PPI) stabilised emulsions at acidic conditions by complexation with dextran sulphate (DS). Soluble and insoluble complexes with different charge and particle size were formed depending on the phase separation behaviour. The surface adsorption of PPI became slower after complexation with DS, but the percentage of adsorbed proteins at the oil–water interface was not affected. The formation of PPI–DS soluble complexes at high content of DS (≥0.4%) significantly improved the negative net charges of PPI, prevented the aggregation of protein, which further improved the emulsifying property of PPI at acidic conditions through the strong electrostatic repulsion and steric hindrance effects. Insoluble complexes with relatively weak net charge and large particles were formed at low DS content (≤0.2%), resulting in the bridging flocculation of oil droplets at pH 5 and 4. Thus, the emulsifying ability of PPI under acidic conditions could be significantly improved by formation of soluble complexes with DS.