Compositional, physico-mechanical and functional properties of two Ghanaian cowpea (Vigna unguiculata) varieties

Abstract

Cowpea (Vigna unguiculata) is an important legume cultivated in many parts of Africa and contributes a significant amount of plant-based protein to human diets. There are many varieties of cowpeas, and these have varying seed characteristics such as shape, size, colour and nutritional properties. The compositional, physico-mechanical and functional properties of two varieties of cowpea seeds were studied in order to establish their full food-use potentials as well as key parameters for their postharvest machinery for processing, handling, and storage. The proximate composition of the two cowpea cultivars was determined using standard methods. Physico-mechanical analyses carried out were the hundred-seed weight and volume, bulk density, true density, size, aspect ratio, surface area, equivalent diameter, porosity and angle of repose. Functional properties determined were cooking time and water uptake of the grain, water and oil absorption, foam capacity and stability, and emulsion capacity and stability. Padi Tuya was longer, broader and thicker than Wang Kae. The results showed both varieties to be a useful source of macronutrients. The moisture, fat and fibre in Wang Kae were significantly higher (p<0.05) than Padi Tuya. However, the cowpea varieties had comparable protein levels with a mean of 17.7 g/100 g. The cooking time, hydration capacities and indices of the two varieties were also significantly different (p<0.05), but their swelling capacities, indices and water uptake indices were comparable. Cooking times were 40 and 62 min for Padi Tuya and Wang Kae, respectively. The flours of the two varieties had comparable water and oil absorption capacities as well as for the swelling indices, but their emulsion capacities and stabilities were significantly different (p<0.05). Padi Tuya had a higher foam capacity with lower stability compared to Wang Kae. The physico-mechanical properties determined would aid in the design of cleaning, handling and other processing machinery as well as storage facilities for the new cowpeas. The functional and the compositional parameters would assist in the food formulations