Structure-function relationships of cowpea (Vigna unguiculata) globulin isolate: influence of pH and NaCl on physicochemical and functional properties

Physicochemical and functional properties of cowpea globulin isolate were determined as a function of pH and NaCl concentrations. Protein solubility (PS) increased with increasing pH from 3 to 8, while at low pH, PS decreased with increasing ionic strength. At low pH and all ionic strengths, the protein isolate was extensively coagulated by heat, while aromatic hydrophobicity, fluorescence intensity and emulsifying activity index were all higher than results obtained at high pH. Emulsion stability was lowest at low pH and ionic strength. Foaming capacity increased with increasing pH and ionic strength. Foam stability was affected more by pH changes than by ionic strength. The results were discussed on the basis of protein-protein and protein-solvent interactions, as affected by the balance between electrostatic repulsions and hydrophobic interactions.