MICROBIAL QUALITY AND HEAVY METAL CONTAMINATION OF SLICED WATERMELON (CITRULLUS LANATUS) FRUITS IN SELECTED MARKETS IN AKURE, NIGERIA.

Abstract

Fruits are extraordinary dietary source of nutrients that are vital for health and well-being. The consumption of sliced watermelon fruit has tremendously increased in Nigeria in the past few years. However, the microbial and heavy metal contamination of this fruit has not been well documented particularly in Akure metropolis. Hence, a cross-sectional study to determine the microbial quality and heavy metal contamination of sliced watermelon fruits was therefore carried out in three selected Markets (Oja-Oba, Isinkan and Shasha) in Akure metropolis. Sliced watermelon fruit samples were randomly purchased from six different vendors in each market while wholesome watermelon fruit served as control. Pour plate technique was used to determine its microbial load. Bacterial isolates were identified using morphological, biochemical and molecular techniques while fungal isolate was identified using cotton in the blue lactophenol method. Atomic absorption spectrophotometry was also used to determine heavy metals: nickel (Ni), cadmium (Cd), chromium (Cr), lead (Pb) and copper (Cu) present in the sliced fruits. The total heterotrophic count of the sliced watermelon fruits from Oja-oba, Isinkan and Shasha markets ranged between 0.00×104 -1.53×105 CFU/g, 0.00×104 -1.40×105 CFU/g and 0.00×104-2.02×106 CFU/g respectively while the mean coliform count also ranged between 0.00×104 -3.90×105 CFU/g, 0.00×104 -7.03×105 CFU/g and 0.00×104-2.70×105CFU/g respectively. Similarly, the fungal count in the sliced watermelon fruit samples from Oja-oba, Isinkan and Shasha markets ranged between 0.00×104-0.33×104 CFU/g, 0.00×104-1.00×104 CFU/g and 0.00×104-1.00×104 CFU/g respectively. The Yeast count for all the samples obtained from Oja-oba, Isinkan and Shasha markets ranged from 0.00×104-4.57×105 CFU/g, 1.33×104-1.70×105 CFU/g and 2.00×104-9.57×105 CFU/g respectively. Salmonella and Shigella were not detected in all the sliced watermelon samples purchased from the selected markets. Five bacteria and one fungal isolated were Escherichia coli, Bacillus cereus, Proteus mirabilis, Providencia rettgeri, Kerstersia gyiorum and Aspergillus niger. For heavy metals contamination, cadmium and lead were not detected in any of the fruit samples. However, nickel and copper were detected in all the sliced watermelon fruit samples, and the values ranged from 0.20-1.42mg/100g and 0.04-0.17mg/100g respectively. The values of nickel present in the samples were above WHO permissible limits (0.20mg/100g) while the levels of copper in the samples were within the WHO permissible limit (0.2mg/100g). Contamination of the sliced watermelon fruits with microorganisms and heavy metals may be due to poor sanitary conditions employed by the vendors during processing and packaging. This, therefore, calls for public awareness programs to educate fruit vendors on personal and environmental hygiene to reduce contamination.