Effect of Cooking Methods on the Nutritional Composition of Cowpea (Vigna unguiculata) Commonly Consumed in Nasarawa State

Cowpea is a protein-rich legume widely cultivated and consumed in North Central Nigeria, with Nasarawa State emerging as one of the leading producing states. Different cooking methods employed by households may differentially affect the nutritional quality of cowpea dishes. This study evaluated the effect of three cooking methods, namely boiling, pressure cooking, and slow simmering, on the proximate composition, mineral bioavailability, and anti-nutritional factor content of white cowpea obtained from Lafia Main Market in Nasarawa State. Each cooking method was applied for standardised durations, and samples were analysed for crude protein, crude fat, crude fibre, ash, carbohydrates, phytates, tannins, iron, and zinc. Results showed that pressure cooking significantly reduced phytate and tannin content by 68 and 60 percent respectively compared to raw cowpea, while best preserving crude protein content at 23.6 percent. Boiling showed intermediate reductions in anti-nutritional factors but greater losses of water-soluble minerals, particularly zinc, into cooking liquor. Slow simmering required longer duration, resulting in the highest tannin retention. In vitro iron and zinc dialysability were highest in pressure-cooked samples. The study recommends pressure cooking as the preferred method for cowpea preparation in Nasarawa households seeking to optimise nutritional benefit while minimising fuel consumption. Keywords: cowpea, cooking methods, anti-nutritional factors, mineral bioavailability, Nasarawa.