Pearl millet porridge : improvement in iron and zinc bioaccessibilities through fortification with micronutrient-rich plant food components

Abstract

The most prevalent micronutrient deficiencies in sub-Saharan Africa are iron, zinc and vitamin A. This is partly due to staple diets composed of mainly cereals, containing high levels of iron and zinc bioavailability inhibitors. In this study, pearl millet porridge was food-to-food fortified with dried micronutrient-rich plant foodstuffs (moringa leaves, hibiscus calyces, baobab fruit pulp), and a mango-carrot premix (plus sunflower oil) as a provitamin A source, and the effect on iron and zinc bioaccessibilities evaluated. The foodstuffs were analysed for mineral and antinutrient contents. The effects of adding 5 and 15 g/100 g, dry basis (db) pearl millet plus provitamin A source of dried moringa leaves, hibiscus calyces or baobab fruit pulp on iron and zinc bioaccessibilities (in vitro dialysability assay) were determined. Baobab fruit pulp, despite containing high levels of tannins (2286 mg CE/100 g, db), increased the iron and zinc bioaccessibilities the most, when added as food-to-food fortificants to pearl millet. This could contribute >200% and >180%, respectively, more to the iron and zinc absolute requirements (defined as the sum of the daily basal losses of the mineral plus the amounts of the mineral needed for growth) than the pearl millet plus provitamin A source porridge, for 2–5-year-old children. Fortification with hibiscus calyces also resulted in substantial increases in iron and zinc bioaccessibilities. This is because baobab fruit pulp and hibiscus calyces contain substantial levels of iron and zinc bioavailability enhancing organic acids. The addition of moringa leaves generally resulted in the lowest increases and, in some cases, even reduced the iron and zinc bioaccessibilities, even though it had the highest level of iron (58.4 mg/100 g, db) of all the plant foodstuffs. Dried moringa leaves had the highest levels of calcium and total phenolics, and substantial levels of phytate, as well as possible low levels of organic acids, all which contributed to the low iron and zinc bioaccessibilities. Including baobab fruit pulp and possibly hibiscus calyces in a cereal based meal, show potential to increase both the iron and zinc bioaccessibilities. The iron and zinc status of people consuming a cereal-based diet may be improved by the inclusion of baobab fruit pulp or possibly hibiscus calyces, as food-to-food fortificants, to cereal-based porridges.