Researchers at the University of Ilorin, Kwara State, have raised the alarm over possible metal contamination of food processed with cast-iron grinding discs commonly used in public mills.
The researchers said their study showed that dry grinding could introduce as much as 1.7 grammes of metallic contaminants into 10 kilogrammes of ground maize, raising concerns about the possible long-term health effects on consumers.
The research was conducted by 10 scholars from different departments of the university and funded by the Tertiary Education Trust Fund under its National Research Fund.
The study, titled, “Documented contamination levels, sources and health risks associated with metallic wear from cast-iron grinding discs commonly used across Nigeria and other developing nations,” examined the level, sources and health implications of metallic particles released during food grinding.
The university’s Director of Corporate Affairs, Kunle Akogun, disclosed the findings in a statement on the research.
The Principal Investigator, Prof. Sulaiman Abdulkareem of the Department of Mechanical Engineering, said the findings showed the need for improved milling practices and stricter quality control of grinding discs used in food processing.
“The average contaminant particle size was approximately 43 micrometres, making the particles small enough to pass into the stomach unnoticed,” Abdulkareem said.
He said the researchers also discovered that dry grinding generated significantly more metallic contaminants than wet grinding.
According to him, the presence of water during wet grinding served as a lubricant, thereby reducing wear on the grinding discs.
The study further found that all the grinding discs examined were susceptible to corrosion when exposed to a simulated gastric solution designed to replicate the conditions in the human stomach.
The solution had a pH of 1.7 and was maintained at 37 degrees Celsius.
“Corrosion occurred at varying degrees among the discs, with the imported sample showing the highest susceptibility, while the pit furnace-produced disc showed the most resistance,” Abdulkareem said.
The research team included Prof. Ismaila Idowu Ahmed, Prof. Jamiu Kolawole Odusote, Prof. Rasheedat Modupe Mahamood, Dr Jeleel Adekunle Adebisi, Dr Segun Isaac Talabi and Taiwo Yahaya from the Department of Materials and Metallurgical Engineering.
Prof. Lawrence Aderemi Olatunji of the Department of Physiology and Dr Mariam Kehinde Sulaiman of the Department of Medical Microbiology and Parasitology provided medical and biological expertise.
Prof. Jamiu Adetayo Adeniran of the Department of Chemical Engineering later joined the team, contributing expertise in environmental source apportionment and health-risk modelling.
The researchers called for stronger quality-control measures and improved milling practices to minimise metallic contamination of food processed in public grinding mills.
