Optimising functional properties during preparation of cowpea protein concentrate

Response surface methodology (RSM) was used for modelisation and optimisation of protein extraction parameters in order to obtain a protein concentrate with high functional properties. A central composite rotatable design of experiments was used to investigate the effects of two factors, namely pH and NaCl concentration, on six responses: water solubility index (WSI), water absorption capacity (WAC), oil holding capacity (OHC), emulsifying activity (EA), emulsifying stability (ES) and foam ability (FA). The results of analysis of variance (ANOVA) and correlation showed that the second-order polynomial model was appropriate to fit experimental data. The optimum condition was: pH 8.43 and NaCl concentration 0.25 M, and under this condition WSI was ⩾17.20%, WAC ⩾ 383.62%, OHC ⩾ 1.75 g/g, EA ⩾ 0.15, ES ⩾ 19.76 min and FA ⩾ 66.30%. The suitability of the model employed was confirmed by the agreement between the experimental and predicted values for functional properties.