Additions of caffeic acid, ascorbyl palmitate or γ-tocopherol to fish oil-enriched energy bars affect lipid oxidation differently

The objectives of the study were to investigate the effects of caffeic acid, ascorbyl palmitate and γ-tocopherol on protection of fish oil-enriched energy bars against lipid oxidation during storage for 10 weeks at room temperature. The lipophilic γ-tocopherol reduced lipid oxidation during storage when added at a concentration above 440 μg/g fish oil. However, the best antioxidative effect was observed when it was added at a concentration of 660 μg/g fish oil. In contrast, prooxidative effects were observed when using either γ-tocopherol at concentrations below 220 μg/g fish oil, or the hydrophilic caffeic acid, or the amphiphilic ascorbyl palmitate at concentrations of 75, 150 and 300 μg/g fish oil. Prooxidative effects were observed as an increase in the formation of lipid hydroperoxides and volatile secondary oxidation products, as well as the development of rancid off-flavours. The differences in the efficacies of the three antioxidants examined are expected to be related to their different localisations and mechanisms of action.