CBN NAIRA

This study investigated the influence of grinding fineness on heavy metal leaching across seven common food matrices-melon, tomatoes, pepper, white and yellow corn, beans, groundnut, and crayfish-using both household and industrial tools. Samples were processed at two fineness levels (coarse and smooth), and analyzed for iron (Fe), manganese (Mn), zinc (Zn), nickel (Ni), cadmium (Cd), and lead (Pb). Results showed that smooth grinding consistently produced higher Fe and Zn concentrations than coarse grinding, indicating that finer particle exposure and increased friction enhance metal transfer from processing tools. Iron levels were highest in beans (10.97 mg/kg), followed by crayfish (6.47 mg/kg) and white corn (4.64 mg/kg), while zinc peaked in crayfish (1.15 mg/kg) and groundnut (0.82 mg/kg). Manganese were moderate, with the highest levels in pepper (0.71 mg/kg) and melon (0.58 mg/kg). Nickel appeared only in isolated smooth-ground samples, while cadmium and lead were largely undetected, except for trace levels in melon (0.015 mg/kg) and tomatoes (0.00008 mg/kg). Blenders, hand crank grinders, and aged milling machines contributed most to metal leaching, whereas traditional tools such as mortars and grinding stones showed comparatively lower contamination. Although detected metal levels generally fell within international food safety limits, cumulative exposure may pose long-term health risks. The study concludes that grinding fineness, tool type, and age are key factors influencing heavy metal migration during food processing. Routine equipment maintenance, use of food-grade materials, and greater public awareness are recommended to minimize contamination and ensure safer household and industrial food processing practices.