7. Effects of Processing Techniques on the Nutritional Quality of Cowpea (Vigna unguiculata L.) Varieties

Abstract

Cowpea is a widely consumed food crop produced in the Savanna zone of Ghana. Anti-nutrients/bio-active compounds in it limit the biological availability of important nutrients/minerals (proteins, carbohydrates, fat, sodium, zinc, calcium, iron e.t.c). This study employed soaking to investigate the nutritional value of three cowpea varieties (Wang Kae, Kirkhouse Benga and Padi-Tuya). The soaking was in two forms; soaking in water and soaking with 1% each of NaHCO3 and NaCl solutions. Standard chemical analytical procedures were carried out to measure proximate parameters (Fat, protein, carbohydrate, ash, moisture and crude fibre), anti-nutrients/bioactive compounds (Tannins, phytates, oxalate and flavonoids), and minerals (Sodium, iron, calcium and zinc) contents of the cowpea varieties. Significant differences (p ≤ 0.05) in proximate composition, anti-nutrients/bioactive compounds and minerals among the cowpea varieties were obtained. Moisture content, ash, crude protein, crude fat, carbohydrates and crude fibre varied among the soaking regimes for the samples in the ranges of 7.47-19.90%, 2.35-6.11%, 23.35-26.33%, 29.23-35.33%, 21.70- 31.36% and 2.24-4.78%, respectively. Values for iron, zinc, calcium and sodium ranged between 24.86-214.46mg/kg, 45.02-216.93mg/kg, 31.12-56.59mg/kg and 34.82-136.13mg/kg, respectively. Tannins, phytate, flavonoids and oxalate values also ranged between 1.35-6.74mg/g, 4.18-10.70mg/g, 15.50- 91.39mg/100g and 13.64-24.63mg/g, respectively. These results indicate that, soaking with water and (NaHCO3 + NaCl) solution have potentialities for enhancing nutritional value in the cowpea varieties, which could be a means of combating nutritional deficiencies and food insecurity in Ghana and other countries in West Africa.