ANTIOXIDANT AND PROOXIDANT ACTIVITY OF GREEN TEA EXTRACTS IN MARINE OILS

The activity of green tea extracts (GTE) on the oxidation of refined, bleached and deodorized (RBD) seal blubber oil (SBO) and menhaden oil (MHO) was examined under Schaal oven conditions at 65 degrees C. Progr ession of oxidation was monitored using weight gain, peroxide value (P V) and 2-thiobarbituric acid-reactive substances (TBARS) data. GTE exh ibited a pro-oxidant effect in both oils examined, perhaps due to the catalytic effect of their chlorophyll constituents. Therefore, in foll ow-up experiments, a column chromatographic technique was employed to remove chlorophyll f'rom GTE. The resultant dechlorophyllized green te a extract (DGTE) was applied to both SBO and MHO at 100, 200, 500 and 1000 ppm levels. The antioxidant activity of DGTE was compared with th e effects of the commonly-used antioxidants such as butylated hydroxya nisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinon e (TBHQ) at 200 ppm and alpha-tocopherol at 500 ppm. DGTE at greater t han or equal to 200 ppm exhibited excellent antioxidant activity in bo th oils and its efficacy was higher than that of BHA, BHT and alpha-to copherol, but less than that of TBHQ. (C) 1998 Elsevier Science Ltd. A ll rights reserved.