Fractionation, solubility and functional properties of cowpea (Vigna unguiculata) proteins as affected by pH and/or salt concentration

The content, fractionation, solubility and functional properties of cowpea proteins were determined. The effects of pH and/or NaCl concentration on some of these functional properties were also investigated. The protein content of the seed was found to be 26.8%. Albumin is the major fraction of cowpea seed proteins. The minimal protein solubility was observed at pHs 4, 5 and 6, and the maximum was at pH 10. The emulsifying capacity, activity and emulsion stability, as well as foaming capacity and foam stability, were greatly affected by pH levels and salt concentrations. Lower values were observed at a slightly acidic pH and high salt concentration. The least gelation concentration of cowpea proteins was found to be 6% when the proteins were dissolved in 0.5 or 1.0 M NaCl. The total protein was highly viscous and dispersable with a water holding capacity of 2.20 ml H2O/g protein, oil-holding capacity of 1.10 ml oil/g protein and bulk density of 0.82 g/ml, while dispensability was found to be 72.0%.