COMPARISON STUDY OF THE EFFECTS OF DIFFERENT CRUDE GREEN TEA POLYPHENOLS ON THE QUALITY OF DRIED CATFISH DURING AMBIENT STORAGE

Abstract

ABSTRACT The comparative antioxidant effect of adding different crude green tea polyphenols (GTP) and vitamin C (VC) on the susceptibility of dried catfish (Clarias gariepinus) quality changes during ambient storage was investigated. Catfish fillet was treated with different concentrations of GTP: 1% NaCl plus 0.01% GTP, 1% NaCl plus 0.03% GTP and 1% NaCl plus 0.01% of VC before drying process. Control muscle sample (CK) was treated only with 1% of NaCl solution (without GTP extract) contained only 1% NaCl, but not GTP. Samples were oven‐dried for 5 days at 45C. The quality change was evaluated over a course of 4 weeks for pH, volatile basis nitrogen, peroxide value, thiobarbituric acid reactive substances and free fatty acid. The results indicated that the most effective antioxidant was GTP and there was no significant differences (P < 0.01) between laboratory‐extracted crude green tea polyphenol and commercial crude green tea polyphenol. This study pointed out that GTP is a good natural antioxidant in comparison with VC and CK, so, it could be easily used in food industry to improve quality and shelf life of food products.PRACTICAL APPLICATIONSFish is a very important foodstuff because of its high protein content and nutritional value. It is also a greatly perishable product, especially in hot climates and tropical areas where cold preservation techniques are often missing and quality losses can occur very rapidly after catch. Addition of antioxidants during drying process can be used to inhibit lipid oxidation and microbial and insect infestation. However, questions regarding the safety of synthetic antioxidants together with consumer's preference have led to increased interest and research on natural antioxidants. Consumers favor natural antioxidants, which may have a positive effect on human health. Green tea polyphenol (GTP) as a natural antioxidant has lower toxicity than synthetic antioxidants like butylated hydroxyanisole and butylated hydroxytoluene, and more effectiveness than VC. It can be used as an alternative to VC to extend the quality of fish and fish products during storage.