Physicochemical, Cooking Quality and Sensory Acceptability of Three Cowpea Varieties Grown in Botswana

Abstract

Background: Information on the physicochemical, cooking and sensory qualities of cowpea seeds are required for nutrition information, to design processing and for consumer acceptance. In view of this, three cowpea varieties (Tswana, Blackeye and ER7) grown in Botswana were evaluated. Method: Proximate compositions, physical, gelatinization and sensory properties respectively were evaluated following AOAC, conventional, Amylograph and on 7-point hedonic sensory acceptability scale. Result: Significant variations (p less than 0.05) were observed in fat, fiber, ash and available carbohydrate (CHO) contents, length, thickness, hundred seeds weight (HSW), hydration capacity, hydration index, cooking time, flour starches maximum gelatinization temperature (Tm,°C) and viscosity at Tm. The percentage moisture, protein, fiber, fat, ash and available carbohydrate contents ranged 9.5-10.1, 21.7-22.8, 2.3-2.6, 1.1-2.0, 2.1-3.0 and 59.4-62.3, respectively. Initial gelatinization temperature (To,°C) and Tm (°C) were ranged 71.3(ER7)-73.7(Tswana) and 83.0(ER7)-84.7(Blackeye), respectively. Significant (p less than 0.05) variations in Tm and viscosity at Tm were observed because of differences in water uptake, swelling and thickening ability at high temperature. Longest cooking time was recorded for Tswana (43.57 min) while shortest was for Blackeye (36.10 min). Tswana recorded a longer cooking time probably because of low water hydration capacity, small seed size and low HSW. There was no significant difference in the sensory liking of the cooked cowpea seeds and were rated from slightly to moderately like. Cowpeas of high protein and fiber contents, short cooking time and high thickening ability on cooking are preferred for healthy diets. In terms of cooking time and thickening ability, Tswana variety appeared poor. Shorter cooking time, high protein content and high thickening ability of Blackeye cowpea is more acceptable. The ER7 is preferred for its large seed size.