Heavy metal health risk assessment and microbial quality of locally milled ready-to-eat tomato in Tamale, Ghana

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This study was carried out with the aim to assess the microbial quality and risks associated with the intake of four heavy metals i.e., lead (Pb), cadmium (Cd), arsenic (As) and mercury (Hg ) via the consumption of ready-to-eat tomato sauce from four (4) milling sites in the Tamale Metropolis . Twelve (12) samples of ready-to-eat tomatoes sauce were collected in triplicates from four (4) milling sites. The samples were digested with nitric and perchloric acid mixture (3:1) and analyzed using Atomic Absorption Spectrometer (AAS). Average concentrations (± SEM) of Cd, Pb, As and Hg in ready-to-eat tomato were found to be 0.1062±0.03330, 0.37085±0.19758, 0.00025±0.00004 and 0.00367±0.00068 mg/kg respectively. The concentrations of Cd and Pb were found to be significantly higher than the tolerable limits. However, concentration of Hg and As were within the permissible limits and thus safe to consume. Generally the level of health risk associated with exposure to the four heavy metals (Cd, Pb, As and Hg) through ingestion of the ready-to-eat tomato was low and does not increase for example cancer risk over a lifetime (70years). However, the mean dietary intake for Cadmium (15.61 µg/kg) and Mercury (47.57 µg/kg) were higher than the Provisional Tolerable Weekly Intake (PTWI) body of 2.5 and 25 µg/kg respectively. Analysis of the food samples also revealed mean total bacterial count to be 7.00 ± 0.46 log10 cfu/g. The minimum and maximum bacterial count ranged from 6.7 ±0.12 log 10 cfu/g to 7.2±0.9 log10 cfu/g respectively. The bacterial species encountered included Bacillus sp. and Staphylococcus aureus. Overall 66% of the samples tested Positive for Escherichia coli, this could be due contaminated processing water, or cross contamination of raw materials and cooked food by equipment or vendors. All the samples had bacterial counts higher than the acceptable levels and thus pose health risk to the local population who regularly patronize them.
A thesis submitted to the institute of Distance Learning, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the award of Master of Science Degree (M.Sc. Food Quality Management)