Impact of traditional processing on proximate composition, folate, mineral, phytate, and alpha-galacto-oligosaccharide contents of two West African cowpea (Vigna unguiculata L. Walp) based doughnuts

Doughnuts made from cowpea, a highly nutritious pulse, are frequently consumed in West Africa. As processing may affect their nutritional composition, cowpea processing into two doughnut types (ata and ata-doco) was characterized, and samples collected from 12 producers in Cotonou, Benin. Proximate composition, folate, mineral, phytate, and alpha-galacto-oligosaccharide contents were determined in the raw material, intermediate products, and doughnuts. Mass balance was assessed during ata production to monitor folate and alpha-galacto-oligosaccharides distribution, and to determine what steps most influenced their concentration. Ata was prepared with dehulled-soaked seeds, and ata-doco with whole or partially dehulled, non-soaked and dry-milled seeds. After both types of doughnuts production, lipid content increased by 11-33 times compared with raw seeds, due to oil absorption during deep-frying. Milling led to an increase of iron content by 50-57 % (ata) and 21-75 % (ata-doco production). Alpha-galacto-oligosaccharide contents decreased by 22-57 % after whipping during ata-doco, but not during ata production. The mass balance assessment showed significant reductions of folate (-50 %) and alpha-galacto-oligosaccharides (-33 %) after dehulled seed washing and soaking during ata production. This study showed that the impact of traditional processing on the nutritional value of cowpea-based doughnuts is strong, but highly variable depending on the doughnut type and producers' practices.