Oxidative stability of fish oil supplemented with carnosic acid compared with synthetic antioxidants during long-term storage

The effects of carnosic acid (CA) of different concentrations (0.1, 0.2, and 0.3 mg/g) and synthetic antioxidants on oxidative stability in fish oil stored for 66 days at different temperatures (30 and 4 °C) were compared. The investigation focused on the increase in peroxide and conjugated diene values, as well as free fatty acid and thiobarbituric acid-reactive substances. The changes in trans fatty acid and aldehyde compound contents were investigated by Fourier transform infrared spectroscopy, while the changes in polyunsaturated fatty acid content were monitored by gas chromatography–mass spectrometry. The results show that the three CA concentrations were more effective in restraining fish oil oxidation, in which a dose–response relationship was observed. The antioxidant activity of CA was stronger than that of vitamin E, but still weaker than that of tertiary-butyl hydroquinone. Fish oil supplemented with 0.2 mg/g CA exhibited favourable antioxidant effects and is preferable for effectively avoiding oxidation.