Comparative Study of Iron, Manganese and Nickel Contamination Potential of Disc and Hammer Milling Equipment and their Toxic Effect on Rat Kidney

Aim: To investigate the effect of hammer and disc milling equipment on the levels of Iron (Fe), Manganese (Mn) and Nickel (Ni) contents in maize (Zea mays) flour and the consequent impact on the kidney of albino rats.

Study Design: The rats were randomly divided into groups of five rats per group. Six of the groups were fed with maize flour milled with a hammer mill, while the other six groups were fed with maize flour milled with a disc mill, and the thirteenth group was fed with crushed flour in a mortar and pestle as a control. The rats were sacrificed by decapitation under anesthesia on the 14th and 28th days.

Place and Duration of Study: Departments of Biochemistry and Histology laboratories of the University of Jos, Nigeria, between, January to June, 2021.

Methodology: For six days, a portion of the maize grains was milled with a hammer mill, another with a disc mill, and a third fraction was crushed into flour with a wooden mortar. The inductive coupled plasma mass spectrophotometric method was used to determine the levels of Fe, Mn, and Ni in maize flour. To avoid lysing the blood, blood samples were carefully collected by allowing it to run down the test tube's wall. The blood was allowed to coagulate at room temperature before being centrifuged and the serum collected and frozen until it was time for biochemical analysis. The kidneys of the rats were excised, cleaned, and preserved in chloroform until histological examinations were required.

Results: The results show that Fe (325.16 ± 30.00 mg/kg and 205.05 ± 30.20 mg/kg) and Ni (20.92 ± 5.92 mg/kg and 18.00 ± 2.70 mg/kg) levels were extremely high in both disc and hammer milling machines. The Fe and Mn values in disc milled maize flour were higher than those in hammer milled maize flour. Rats in all groups had significantly higher serum urea, creatinine, K+, Na+, and Cl- levels than the control group. The kidney tissues of all the rats in the control and hammer-milled flour groups were normal, except for group 1 of the disc mill, which showed mild damage, according to the histopathological analysis.

Conclusion: The Day 1 group fed with disc-milled flour showed a dense cast, atrophy, and nuclei loss in their kidney tissue. According to the results of the study, hammer milled maize flour is less harmful than disc milled maize flour, as shown by kidney histopathology.