Antioxidant activity of green tea and its catechins in a fish meat model system

The antioxidant activity of ground green tea (GGT) and commercial tea extracts, namely Polyphenon 25 (P-25), Polyphenon 30 (P-30), Polyphenon 60 (P-60), and Nikken Polyphenon 60 (NPP-60), as well as green tea extracts (GTE) prepared on laboratory scale and pure tea catechins, namely, (-)epicatechin (EC), (-)-epigallocatechin (EGG), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate (EGCG), in a fish meat model system was evaluated. Results so obtained were compared with those of samples containing commonly used antioxidants Such as alpha-tocopherol, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and tert-butylhydroquinone (TBH&). The ground white muscle of mackerel (model system) was cooked at 75 degrees C and stored at 4 degrees C for 7 days. Progression of oxidation was monitored by measuring changes in the 2-thiobarbituric acid-reactive substances and selected and/or total volatile contents of samples. The samples treated with GGT leaves, tea extracts, and pure catechins showed excellent oxidative stability as compared with samples that contained alpha-tocopherol, BHT, BHA, and TBHQ. The potency of catechins in the prevention of oxidation in fish meat was in the decreasing order EGCG approximate to ECG > EGC much greater than EC. However, EGCG was more effective (p < 0.05) than TBHQ, as reflected in total volatile and propanal contents in the system studied.