Assessment of Heavy Metals Introduced Into Food Through Milling Process: Health Implications

ABSTRACT

The present study was conducted to characterised and assess heavy metal contamination in food through milling process and their health implications. Grinding plate made from Ghana, India and Nigeria purchased from the Ghanaian open market were used for this work. Maize from the same farm was milled into flour using the three grinding plates inserted into three different corn milling machines operating on commercial bases. The first grinding was done immediately after the insertion of the newly sharpened plates into the machines. The plates were left for continuous daily usage. Subsequent milling of the maize was done after intervals of one month. The grinding plates and maize flour was analysed using Atomic absorption spectrophotometer (AAS). The results recorded indicated that the heavy metals content of the Ghanaian, Indian and Nigerian made plates had the similar metal contents but varied in terms of the individual metal concentrations. Flour from the Ghanaian made plates had the highest level of contaminants with the least from that of the Indian made plates. Generally the highest levels of contamination were observed in the first milling for the three plates as compared to the three subsequent milling at monthly intervals. The contamination levels showed a decreasing trend from the first month (first milling) to the fourth month (fourth milling). Cu, Cr and Ni showed concentrations above the permissible limit set by FAO/WHO in milled maize using Ghanaian made plate. Copper (Cu) recorded a concentration value between 15.04 mg/kg to 10.21mg/kg, 11.25 mg/kg to 9.13mg/kg and 10.36mg/kg to 9.68mg/kg using the Ghanaian-, Indian and Nigerian made plate respectively. Chromium (Cr) recorded a concentration between 1.51 mg/kg to 0.96 mg/kg, 1.03 mg/kg to 0.91 mg/kg and 0.98mg/kg to 0.80 mg/kg using Ghanaian-, Indian and Nigerian made plates respectively. Nickel (Ni) recorded a concentration value between 23.23 mg/kg to 10.43 mg/kg, 11.46 mg/kg to 10.43 mg/kg and 12.55 mg/kg to 10.09 mg/kg Using Ghanaian-, Indian and Nigerian made plates respectively. Which shows that the Cu, Cr and Ni concentration decreases from the first month (first milling) to the fourth month (fourth milling).The Ghanaian made plate was found to wear faster relative to Nigerian- and Indian made plate with that of showing the least rate of wear. The Ghanaian made plates was found to cause more contamination than the other two but generally, the Indian made plates caused least contamination. The Indian made plates had the least Cd and Pb concentration levels. The elemental concentration and the risk assessment calculations have shown that contamination of milled products are highest within the first month of the use of the grinding plates but can decreases considerably with time. The HRI value for first milled maize with locally made grinding plate showed human health problem for Cr and Ni metals contaminations in the maize flour.