Iron contamination during in-field milling of millet and sorghum

Nutritionally, contaminant iron in foods may lead to overestimation of the satisfaction of iron requirement while iron deficiencies remain a widespread health problem. Iron contamination was measured in millet and sorghum grains after decortication and in-field milling using different equipments in Burkina Faso. Total iron content did not change significantly after decortication, probably due to a balance between losses resulting from the removal of iron-rich peripheral parts and contamination. Total iron contents increased significantly after mechanical milling irrespective of whether iron or corundum grindstones were used. Contamination was highly variable, ranging from 3 to 6 mg iron/100 g DM, and was mainly due to wear of the milling equipment. After in vitro digestion of traditional cereal dishes prepared with iron-contaminated or uncontaminated flours, the contaminant iron was found mainly in the insoluble fraction. Only in sorghum was a small proportion (4%) bioaccessible, showing that contaminant iron has poor nutritional interest.