World Journal of Dairy & Food Sciences 13 (2): 94-98, 2018 ISSN 1817-308X © IDOSI Publications, 2018 DOI: 10.5829/idosi.wjdfs.2018.94.98 Corresponding Author: Nora Ibrahim , Zoology Department, Faculty of Science, Cairo University, Cairo, Egypt. . 94 Effect of Freezing and Different Cooking Methods on Heavy Metals Content of the Nile Tilapia Oreochromis niloticus Nora Ibrahim, Manal El-Garhy, Amr Abdel-Khalek, Kareem Morsy and Ali Al Ghamdi 1 1 1 1,2 3 Department of Zoology, Faculty of Science, Cairo University, Cairo, Egypt 1 Department of Biology, College of Science, King Khalid University, Abha, Saudi Arabia 2 Department of Biology, College of Science, Al Baha University, Al Baha, Saudi Arabia 3 Abstract: The Nile tilapia (Oreochromis niloticus) is a species of tilapia, a cichlid fish native to Africa from Egypt south to east and central Africa; it is one of the most commercially important fish species in Egypt. The present study aimed to evaluate the effects of traditional cooking (Fried and grilled) and freezing processes on the concentrations of Cd, Cu, Fe and Pb in fish fillets of O.niloticus. It was observed that in general, the heat treatment by either frying or grilling and freezing of polluted O. niloticus fish flesh led to a decrease of the heavy metals content in all the tested fish parts. The decrease of metals which occurred during frying of fish was lower than that detected after the grilling process. Cadmium concentrations (mg/kg dry wt) after the present experiment were: Fresh flesh (0.142)> frozen (0.031) > fried (0.027) > grilled (0.014). For Cu: Fresh flesh (14.905) > frozen (0.936) > fried (0.696) > grilled (0.311). For Fe: Fresh flesh (9.78 ) > frozen (5.890) > fried (3.085) > grilled (2.998). And for Pb: Fresh flesh (0.058) >fried (0.053) > grilled (0.038) > frozen (0.021).The reduction in the metal contents of the fish during cooking may be related to the release of these metals with the loss of water as free salts, possibly in association with soluble amino acids and coagulated proteins. Therefore, it is possible to reduce the metal in fish parts by choosing a suitable method of cooking. Grilling had a more pronounced effect on the heavy metals content in fish parts than frying. Key words: Oreochromis Niloticus Freezing Cooking Fillet Heavy Metals INTRODUCTION low concentrations, particularly in soft-water Fish constitute a major source of protein and healthy water to higher levels in fish tissues [10]. Evidently these lipid throughout the world and its consumption has metals accumulate frequently in fish flesh [11-14] and increased globally in the recent time. Fish provides the internal organs [15-18]. Many elements, which are present long-chain polyunsaturated omega-3 fatty acid which in sea food, are essential for human life at low might favorably improve lipid profile and reduce concentrations but they can be toxic at high cholesterol levels, the risk of coronary heart diseases, concentrations. Therefore, many consumers regard any stroke and preterm diseases [1-3]. Environmental pollution presence of these elements in fish as a hazard to health represents a major problem in both developed and [19]. The heavy metals concentrations of fish fillets can be underdeveloped countries. Egypt is one country which affected by processing or cooking methods and therefore, suffers from high biosphere pollution (air, soil and water). it is important to determine the concentrations of heavy Many ecological changes occur in water as a result of metals in raw and cooked fish fillets and it is possible to human activities, including agricultural, industrial and reduce the heavy metal concentration in fish fillets by municipal wastes [4].Cadmium (Cd), copper (Cu), lead (Pb) choosing a suitable method of cooking [20-22]. Therefore, and zinc (Zn) salts are usually found in agricultural and it is important to determine the concentrations of essential industrial liquid wastes [5-8] which are discharged into and nonessential metals in raw and cooking fish in order water resources. These metals are toxic to aquatic life at to evaluate the possible risks of fish consumption for environments [9]. Such metals may be accumulated from