Determination of Heavy Metals and Biological Contaminants Present in Locally Processed Tomato, Pepper and Onion Puree Samples from Maiduguri Metropolis, Borno State, Nigeria

Abstract

Contamination of food by heavy metals and microorganisms often occurs right from the farmlands and during processing. This endangers health by predisposition to diseases and factors that can initiate carcinogenesis. The levels of heavy metals and microbial contaminants in tomato, pepper and onion puree processed in some commercial milling points in Maiduguri metropolis was assessed. Twenty samples were obtained by random selection and analyzed for heavy metals by atomic absorption spectroscopy. Samples were cultured on nutrient, blood, MacConkey and mannitol salt agar media for 72 hours using streak plate method. The concentrations of heavy metals were within the range: mercury (0.158 ± 0.10 to 0.321 ± 0.27 mg/L), lead (0.167 ± 0.08 to 0.317 ± 0.25 mg/L), nickel (0.222 ± 0.11 to 0.574 ± 0.23 mg/L) and copper (0.032 ± 0.03 to 0.057 ± 0.03 mg/L) while cadmium was not detected in all the samples analyzed. Three pathogenic gram-negative (Escherichia coli Klebsiella species and Proteus mirabilis) and two less pathogenic gram-positive bacteria (Bacillus subtilis, Coryne bacterium specie) were isolated from the samples. The detection of very low concentrations of heavy metals was within WHO safety limits, while the presence of pathogenic bacteria rises concern over the health status of the general public. There is need to create awareness about good hygiene practices to operators of commercial milling machines within the study area.