EFFECTS OF ADDED CRUDE GREEN TEA POLYPHENOL ON THE LIPID OXIDATION OF COMMON CARP (CYPRINUS CARPIO L.) AND CATFISH (CLARIAS GARIEPINUS BURCHELL) DURING REFRIGERATED STORAGE

The antioxidant activity of crude green tea polyphenol (GTP) on the lipid oxidation of carp (Cyprinus carpio L.) and catfish (Clarias gariepinus Burchell) was investigated. Each fish was trimmed to remove scales, head, fins, tail, viscera, bones, visible fat and skin, and treated with different concentrations of GTP 0.01, 0.03, 0.05 and 0.01% of vitamin C (VC). Control muscle sample (CK) contained no antioxidant. Lipid oxidation was evaluated over a course of 9 days and using a 3-day periodical interval analysis for peroxide value, thiobarbituric acid-reactive substances and free fatty acid. Carp minced fillet containing 0.03% GTP showed the best characteristics (P < 0.05) in relation to oxidative stability. For catfish, 0.05% GTP concentration was more effective in delaying lipid oxidation, when compared with the control sample and VC. However, 0.01%-treated minced fillet with VC was less effective than 0.01% GTP in reducing lipid oxidation. These results demonstrate that tea polyphenols inhibited lipid oxidation, and are effective alternatives to VC in food industry. PRACTICAL APPLICATIONS Green tea polyphenol (GTP) is a natural antioxidant. It can improve the quality of food products during refrigerated storage because of the presence of catechin in its composition. GTP promotes health by preventing lipid oxidation, and has been shown to possess antibacterial and antiviral characteristics. In food industry, it can be used as alternatives to the synthetic antioxidants because the use of these types of antioxidants is controlled nonetheless because of their carcinogenic potential.