EVALUATION OF ANTIOXIDANT ACTIVITY OF ROSEMARY EXTRACTS, CARNOSOL ANDCARNOSIC ACID IN BULK VEGETABLE-OILS AND FISH-OIL AND THEIR EMULSIONS

The antioxidant effectiveness of two rosemary extracts, carnosol and c arnosic acid, was significantly influenced by the type of system teste d (bulk oils vs oil-in-water emulsions), by the oil substrates, the me thods used to follow oxidation, and the concentrations of test compoun ds. The rosemary extracts and compounds effectively inhibited conjugat ed diene hydroperoxide formation in corn oil, soya bean oil, peanut oi l and fish oil, when tested in bulk. Test compounds also inhibited hex anal formation in bulk vegetable oils, and propanal and pentenal forma tion in bulk fish oils. In contrast, these test compounds were either inactive or promoted oxidation in the corresponding vegetable oil-in-w ater emulsions. In fish oil emulsions, however, the rosemary compounds inhibited the formation of conjugated diene and pentenal but not that of propanal. Interfacial phenomena may explain why the hydrophilic ro semary antioxidants afford more protection in the bulk oil systems by being oriented in the air-oil interface, and less protection in the oi l-in-water emulsion systems by partitioning into the water phase.