Effect of Soaking and Boiling on Anti-Nutritional Factors of Cowpea in Kebbi State

Cowpea (Vigna unguiculata) is a major legume crop and protein source in Kebbi State, North West Nigeria, but its nutritional benefits are partially offset by anti-nutritional factors including phytates, tannins, trypsin inhibitors, and haemagglutinins. This study investigates the effect of soaking duration and boiling time on the anti-nutritional factor content of two cowpea varieties, Oloyin and IT99K-573-2-1, sourced from farms in Birnin Kebbi. Cowpea seeds were subjected to soaking treatments of 6, 12, and 18 hours followed by boiling for 20, 40, and 60 minutes in a full factorial design. Phytate, tannin, trypsin inhibitor, and haemagglutinin contents were determined using standard analytical methods. Protein digestibility was measured using an in vitro pepsin digestion assay. Results showed that soaking for 12 hours followed by boiling for 40 minutes reduced phytates by 74 percent, tannins by 81 percent, trypsin inhibitors by 93 percent, and haemagglutinins to undetectable levels. The combination also increased in vitro protein digestibility from 65 to 85 percent. No significant difference in anti-nutritional factor reduction was observed between the two cowpea varieties. The study draws on recent literature on legume processing for improved nutritional bioavailability. Findings provide practical guidance for household-level cowpea preparation and for industrial processors developing cowpea-based protein products in Kebbi State. Keywords: cowpea, anti-nutritional factors, soaking, boiling, protein digestibility