Factors affecting protein extraction from cowpea

Cowpea proteins were extracted using distilled water or ordinary tap water or sodium chloride (NaCl) (0.5 or 1.0 M), at varied extraction times and flour to solvent ratios. Maximum protein extractability was 81% for distilled and tap water, 76.4 and 78.1% for 0.5 and 1.0 M NaCl, respectively. Optimum extraction time varied with solvent nature; it was 30 min for water and 150 min for NaCl, when the flour to solvent ratio was maintained at 1:25. The nitrogen solubility for cowpea proteins was 94.8% at pH 11 and 56% at pH 1. The minimum nitrogen solubility of 11% was obtained at pH 4. The total protein content of cowpea was found to be 26.0%.