Influence of altered solvent environment on the functionality of pigeonpea(Cajanus cajan) and cowpea (Vigna unguiculata) protein isolates

Functional properties of pigeonpea and cowpea isolates were determined as a function of pH and NaCl concentrations. At low pH, nitrogen solubility dec reased with increasing NaCl concentration whereas, at high pH, it increased . Addition of NaCl to the solvent medium resulted in a marginal improvement and a significant improvement, in the emulsifying activity and emulsion st ability of pigeonpea isolate, respectively. The above treatment decreased t hese properties for the cowpea isolate. Varying both the pH and NaCl concen trations resulted in significant improvements in the emulsifying properties of the isolates relative to the control treatment. NaCl concentrations hig her than 0.1 M significantly (P < 0.05) increased the expansion of pigeon a nd cowpea protein-stabilized foams but reduced foam stability, and adjustin g pH from 2 to 8 improved foam expansion but decreased foam stability. Vary ing both the pH and salt concentration had similar effects on the foaming p roperties of the isolates. The least gelation concentration (LGC) of the is olates decreased with increasing salt concentration. Adjusting the pH to va lues away from the apparent isoelectric point, elicited similar responses i n LGC. In 0.5 M NaCl solution, adjusting the pH to 2, 6 and 8 resulted in s ignificant reductions in LGC relative to the distilled water protein suspen sions. (C) 2000 Elsevier Science Ltd. All rights reserved.