Overview
Mugume and colleagues sampled maize flour from eight commercial hammer mills (four diesel, four electric) in Mbarara city and from maize pounded in wooden or metallic mortars. They measured nine metals by flame AAS to see whether milling adds metals, and estimated health risks. Table 1 gives mean ± SD for each mill or mortar.
Key numbers
- Lead: 0.53 to 0.58 mg/kg in all eight hammer mills, 0.55 mg/kg with a wooden mortar and 10.20 mg/kg with a metallic mortar (Table 1, p. 303).
- Cadmium: 0.51 to 0.60 mg/kg across mills; 0.85 mg/kg with the metallic mortar (Table 1).
- Iron: 15.80 to 16.73 mg/kg (diesel mills) and 19.23 to 19.39 mg/kg (electric mills) vs 11.60 mg/kg (wooden mortar) (Table 1).
Methods (brief)
Pooled flour was oven-dried at 85 °C, digested with perchloric and nitric acids and read by flame AAS. Spike recoveries were 98 to 100%. No detection limits or reference materials are reported.
Evidence Fitness
A useful processing comparison, especially the large lead increase from a metallic mortar (two samples only). However, lead, cadmium, chromium, cobalt and nickel sit at 0.5 to 0.6 mg/kg in nearly every group, including the wooden-mortar control the text calls “traces”; this pattern suggests a reporting floor of flame AAS rather than real differences, so the mill values for these elements are uncertain. Maize flour is a proxy for corn-grits, corn-tortilla, cornbread and tortilla-chips; those pages are not linked.