Emulsifying properties of chickpea protein isolates: Influence of pH and NaCl

Structure and emulsifying properties of chickpea protein isolates (CPI) as a function of protein concentration, oil volume, pH and ionic strength were studied. The optimum protein concentration 2 g l−1 used to determine the emulsifying properties was obtained. Emulsifying activity index (EAI) increased from 244 to 376 m2 g−1 with pH from 3.0 to 11.0 except the protein isoelectric point (pI 5.0), where the EAI was 20 m2 g−1 and emulsion droplet size was the largest. At lower ionic strengths (0.0–0.1 M NaCl, pH 7.0), EAI decreased from 253 to 72.4 m2 g−1; however, it increased from 72.4 to 231.4 m2 g−1 at higher ionic strengths (0.1–1.0 M NaCl). A positive relation between EAI and surface hydrophobicity (S0) of CPI at various ionic strengths was obtained, while EAI was independent of S0 under different pH values. α-Helix was the major configuration of CPI at the pI or lower ionic strength.