Effect of Post-Dehulling Treatments on Anti-Nutritional and Functional Properties of Cowpea (Vigna Unguiculata) Flour

Abstract

Recently, cowpea (Vigna unguiculata) has been cited for imparting specific positive health potentiating responses when properly positioned in the diet. However, inherent anti-nutritional factors in cowpea have long been recognized as concerns and require appropriate processing conditions to ameliorate adverse effects. The study focuses on effect of post-dehulling treatments on anti-nutritional and functional properties of cowpea flour. Three genotypes of cowpea (IT99K-573-2-1, IT96D-610, and IT07K-292-10) were dehulled. Dehulled cowpeas were boiled, roasted or autoclaved and prepared into flour. Raw (dehulled) cowpea genotype served as control. Anti-nutritional and functional properties of the products were determined using standard procedures. Antinutrient concentration of cowpeas differed significantly (p≤0.05) among genotypes. Tannin, phytate and oxalate concentration ranged from 31.15 to 121.80g/kg, 22.31 to 48.04 g/kg and 0.01 to 0.026g/kg respectively. Coloured beans (IT96D-610), had significantly lower anti-nutritional content than those of white beans (IT99K-573-2-1 and IT07K-292-10). All heat treatments significantly reduced the levels of  investigated anti-nutrients compared to their respective control. Water absorption capacity and oil absorption capacity were found in the range of  2.12–3.07 mL/g and 1.37-1.73 mL/g, respectively. Swelling power, starch solubility, loose bulk density and packed bulk density varied between 10.79 to 18.42g/g, 0.16 to 1.52g/g, 0.64 to 0.73g/mL and 0.84 to 0.94 g/mL respectively. Colour parameters (L*, a*, b*, hab, C*) showed significant  variations among the genotypes. The combined varietal and processing variation induced significant modification in the inherent anti-nutrients and functional properties of dehulled cowpea as attested by the highly significant (p≤0.05) correlations observed. Processing of cowpea seeds in these forms presents an opportunity for extending their use beyond the dehulled seeds in food system.

Keywords: Cowpea, dehulling, treatment, nutrients, functionality