The effect of culinary treatment on reducing mercury (Hg) concentration in fish was studied with 35 samples of 14 the most common fish species from the South African market. An analytical determination of Hg was carried out by direct thermal decomposition (DTD) of fish samples using a Model RA-915+ Zeeman Mercury analyzer. The Hg concentration in fish had been determined before and after traditional ways of cooking (boiling, poaching, simmering, deep frying and grilling on coal fire) on a dry basis to avoid uncertainty of different water content in cooked and uncooked fish. It was found that the Hg concentration in most cooked fishes (60%) was not changed in comparison with uncooked samples. The cooking procedure, which could reduce Hg concentration by 10-26.3%, is the fish treatment with vegetable brines or lemon juice, possibly, due to formation of soluble complexes of Hg2+ ions with citric acid. The other cooking procedure, which allows lowering the amount of Hg up to 26.5% is the thermal treatment of fish by grilling. The removal of Hg can be explained by a process, which is called “steam distillation”, when fish oil is evaporated at a temperature of boiling water together with methylmercury (MeHg).
N. A. Panichev, S. E. Panicheva