Effects of variety and culture site on nutritional composition of cowpea in Burkina Faso.

Cowpea is a legume, rich in protein, B vitamins and minerals (magnesium, zinc), but also rich in antinutritional factors such as α-galactosides and phytic acid. The nutritional composition of cowpea seeds is therefore a criterion that should be taken into account to improve varietal selection. The nutritional composition of 13 varieties of cowpea cultivated in Burkina Faso was characterised in order to identify varietal selection criteria based on nutritional potential. Nine varieties were cultivated in Tenkodogo (T), 10 in Kamboinsé (K), and 6 in both localities. Protein content were determined by the Kjeldahl method, mineral content by ICP-OES, thiamine content by UHPLC-FLR, phytic acid content by HPAEC-CD and α-galactosides and low-molecular-weight sugars content were quantified by HPAEC-PAD. Variance analysis allowed to evaluate the effect of variety using results obtained in each site (nT=9, and nK= 10), as well as effect of locality using results from varieties cultivated in both sites. The protein contents of the samples studied vary between 19,9 and 26,2 g/100 g DM depending on the variety. The phytate content was higher on the Kamboinsé plot (with results ranging from 0,70 to 1,17 g IP6/100 g DM) than on the Tenkodogo plot (0,42 to 0,80 g IP6/100 g DM). Thiamine equivalent contents, ranging from 0,34 to 0,73 mg/100 g DM, showed a significant variety and plot effect. The main forms of thiamine (di-phosphate and hydrochloride thiamins) were present in variable proportions depending on the variety and the plot. Iron and zinc content were mainly affected by variety and varied between 3,70 to 5,92 mg/100 g DM and from 3,30 to 5,14 mg/100 g DM respectively. The total α-galactoside content was between 3,27 and 6,09 g/100 g DM, and the sucrose content ranged from 1,29 to 5,80 g/100 g DM, both influenced by variety. All components were also influenced by the interaction between variety and plot. Results of nutritional composition should be related to agriculture and processing practices to identify processes decreasing antinutritional factors (α-galactosides, phytic acid) while taking account consumers preferences. Phyate, iron, zinc, thiamin, α-galactoside contents could constitute additional criteria in varietal selection of cowpea, in Burkina Faso.