EFFECTS OF DIFFERENT COOKING PROCESSES ON BIOAVAILABILITY OF MERCURY AND ARSENIC IN EXPOSED AFRICAN CATFISH (Clarias gariepinus, Burchell, 1822)

Fish consumption is one of the major routes of human exposure to environmental contaminants. This study was conducted to assess alternative ways of reducing the bioavailability of mercury and arsenic in Clarias gariepinus and to evaluate ameliorating effects of cooking processes (boiling, frying, and roasting) on the bioavailability of these metals in exposed Catfish. Thirty-six Clarias gariepinus (3 months; 100g-150g; 10-15cm length) were randomly divided into three groups (n=12). 0.2mg/L of mercury chloride and 20µg/l were used as test salts for Mercury (group A) and Arsenic (group B) respectively while Group C was the control. Exposed fish were subjected to various cooking processes on a 7 days interval basis for four consecutive weeks after which they were digested before analysis. The levels of mercury and arsenic in fish samples were determined using titrimetric methods and atomic absorption spectrophotometer (AAS) respectively and the data were analyzed using analysis of variance and the least significant difference (LSD) was accepted at p=.05. A statistically significant difference (p=.05) was observed as a reduction in the mercury level of the processed fish across the weeks as compared with the raw sample and in this order: raw>roasted>fried>boiled. For arsenic-treated fishes, there was no statistically significant difference (p=.05) across the weeks, but an increase in concentration was observed in processed samples as compared with raw samples for the four weeks and in this order: raw<roasted<fried<boiled. None of the cooking procedures has glaring reduction effects on both Mercury and Arsenic. The liver also recorded the highest concentration of both Mercury and Arsenic followed by gills and Muscle of Catfish samples. Since this study and others alike have established little effects of cooking procedures on heavy metals in food, further studies need to be conducted using combined cooking methods at different conditions designed at mitigating the effects of heavy metals in food.