Protection of α-tocopherol in nonpurified and purified fish oil

Menhaden oil was purified by column chromatography to remove minor components. The effect of alpha -tocopherol (alpha TOH) (50-500 ppm) on the rate of formation of hydroperoxides in the original menhaden oil and in the purified menhaden triacylglycerol (TAG) fraction was studied at 30 degreesC in the dark. An increase in the initial rate of formation of hydroperoxides was observed at alpha TOH concentrations above 100 ppm in both substrates. The original menhaden oil oxidized more rapidly than the purified menhaden TAG at all antioxidant levels tested, and the presence of minor components in the menhaden oil was found to contribute only to a limited extent to the peroxidizing effect of alpha TOH. The alpha TOH did not display any prooxidant activity at either of the concentrations tested when the control oil was the purified menhaden TAG. Addition of ascorbyl palmitate eliminated the initial peroxidizing effect of alpha TOH, and this emphasizes the participation of the alpha -tocopheroxyl radical in the reactions causing an accumulation of hydroperoxides at high concentrations of alpha TOH.