Effect of processing on the proximate composition and functional properties of cowpea ( Vigna unguiculata) flour

Abstract

The proximate composition and functional properties of raw, germinated, fermented and heat-treated cowpea flour were studied. The functional properties investigated were protein solubility, water and fat absorption, bulk density, foam capacity and stability. Germination increased the crude protein, iron and total phosphorus but decreased the carbohydrate, fat and total polyphenols content. Protein solubility was pH-dependent with a minimum at pH 4·0. Maximum protein solubility (0·39 mg/ml) was recorded for germinated flour which also showed excellent fat absorption properties. The water absorption capacity of the heat-treated cowpea flour was significantly higher ( P < 0·05) than those of raw, germinated or fermented samples. Bulk densities of the germinated and fermented flours were reduced by 70·6% and 35·3% respectively. The foam of the raw flour was more stable than those of the processed samples. Incorporation of NaCl up to 0·2 m improved the foam capacity of the raw and processed flours. Calculated on a crude protein basis, raw cowpea flour showed comparatively better water and fat absorption properties than raw winged bean or soyflour and hence it may find useful applications in fabricated foods such as bakery products and ground meat formulations.