COWPEA PROTEINS .1. USE OF RESPONSE SURFACE METHODOLOGY IN PREDICTING COWPEA (VIGNA-UNGUICULATA) PROTEIN EXTRACTABILITY

Response surface methodology was used to establish optimum conditions for extracting the protein nitrogen of cowpea meal (Vigna unguiculata). Water, 0.01 M NaOH, 0.5 M NaCl, 70% ethanol, and phosphate buffer (pH 7.0) were used as solvents. Parameters examined included meal-solvent ratio, extraction time, and temperature. The extracts obtained were analyzed for total and nonprotein nitrogen. Maximum extraction (83 %) was predicted with 0.01 M sodium hydroxide. The regression equations obtained gave good predictions of cowpea protein extractability in all solvents. Defatting the cowpea flour resulted in a slight increase in the predicted nitrogen extractable. Preliminary experiments indicated that the pH and ionic strength of the extracting buffer influenced nitrogen extractability. The highest yields occurred at pH 12.0 (96%) and an ionic strength of 1.0 (76%). © 1979, American Chemical Society. All rights reserved.