Effect of pH on the functional behaviour of pea protein isolate–gum Arabic complexes

The functional behaviour (solubility, emulsifying and foaming properties) of pea protein isolate (PPI) and gum Arabic (GA) mixtures were investigated as a function of pH (4.30–2.40) within a region dominated by complex coacervation. Emulsion stability was also investigated using a one- and two-step emulsification approach. Complex coacervation was monitored by turbidimetric acid titration at a 2:1 PPI–GA ratio to reveal the formation of soluble (pH 4.23) and insoluble (pH 3.77) complexes, maximum biopolymer interactions (pH 3.60), and dissolution of complexes (pH 2.62). Emulsion stability was greater for mixed systems relative to PPI alone at pHs between 3.10 and 4.00, and in those prepared using the one-step method. Foam expansion was independent of both biopolymer content and pH, whereas foam stability was improved for the mixed system between pH 3.10 and 4.00. The pH-solubility minimum was broadened relative to PPI to more acidic pHs. Findings suggest that admixtures of PPI and GA under complexing conditions could represent a new blended food and/or biomaterial ingredient.