Effect of extrusion cooking in combination with food-to-food fortification on the mineral bioaccessibility of African-type pearl millet-based porridge

Mineral deficiencies, especially iron and zinc, are still prevalent in urban as well as rural communities among women and children across Africa, including the Sahel. Here, effects of extrusion cooking in combination with food-to-food fortification (FtFF) with plant foods rich in minerals (moringa leaf powder) and their bioavailability enhancers, organic acids (baobab fruit) and β-carotene (carrots, mango, papaya) and additionally micronutrient premix fortification on iron, zinc and other mineral bioaccessibilities in wholegrain pearl millet-based porridges in comparison to their conventionally wet-cooked equivalents were investigated. Percentage bioaccessible iron in extrusion-cooked porridges FtFF with moringa+baobab+carrots+mango, baobab+carrots+papaya and together with micronutrient premix was generally similar to their conventionally cooked FtFF-porridge equivalents. However, the amount of bioaccessible iron in the extrusion-cooked FtFF-porridges was some three times higher. Iron contamination through solubilization from the extruder parts was responsible. Percentage and amount of bioaccessible zinc of the extrusion-cooked FtFF-porridges was substantially increased. This is likely due to phytate degradation during extrusion cooking, thereby reducing the phytate's mineral-chelating effects. Concerning calcium and magnesium, there was no positive effect of extrusion cooking on their bioaccessibility when compared to conventional cooking. However, FtFF substantially increased the amount of bioaccessible calcium and magnesium in the conventionally- and extrusion-cooked FtFF-porridges because of their high contents in moringa and baobab. Consumption of extrusion-cooked ready-to-eat FtFF-porridges, especially when additionally conventionally fortified, is promising to significantly improve bioaccessible iron and zinc in the diet of at-risk African populations, particularly in urban communities.