Improving Nutritional Quality of Cowpea ( Vigna unguiculata ) by Soaking Process

Effect of soaking in water and acetic acid solutions to improve nutritional qualities of cowpea was studied. Cowpeas were soaked in tap water, 1 and 2% acetic acid solutions at 4, 8, 16 and 24 hours. Afterwards, phytates and minerals (Fe and Zn) content were quantified. the phytates content of soaked cowpea grain decreased with the acidity of the soaking solution and the duration of treatment. Compared to the raw material, phytates content decrease by 1.48 to 37.59% in samples soaked in tap water at 4 to 24 hours. Likewise, the phytates content decrease by 7.98 to 41.69 in samples soaked in 1 and 2% acetic acid solution at the same soaking time. The best reduction of phytates content (41.69%) is obtained with acetic acid 2% within 24 hours. Regarding minerals, a slight variation with soaking time in their content was obtained. Acetic acid solutions induced a significant removal of zinc but not for iron. The results revealed that for the two treatment, soaking with vinegar for 24h allows a better reduction of phytates with the best bioavailability of iron but low for zinc; soaking in tap water during 24h gives a good bioavailability for iron and a moderate one for zinc.So, we can say that, if intention is to obtain a product rich in iron with less phytates, it is preferable to use 2% acetic acid for 24h which can be adopted in households.