Inhibition of oxidation in 10% oil‐in‐water emulsions by β‐carotene with α‐ and γ‐tocopherols

The effects of low concentrations of β‐carotene, α‐, and γ‐tocopherol were evaluated on autoxidation of 10% oil‐in‐water emulsions of rapeseed oil triacylglycerols. At concentrations of 0.45, 2, and 20 µg/g, β‐carotene was a prooxidant, based on the formation of lipid hydroperoxides, hexanal, or 2‐heptenal. In this emulsion, 1.5, 3, and 30 µg/g of γ‐tocopherol, as well as 1.5 µg/g of α‐tocopherol, acted as antioxidants and inhibited both the formation and decomposition of lipid hydroperoxides. Moreover, at a level of 1.5 µg/g, γ‐tocopherol was more effective as an antioxidant than α‐tocopherol. At levels of 0.5 µg/g, both α‐ and γ‐tocopherol significantly inhibited the formation of hexanal but not the formation of lipid hydroperoxides. Oxidation was effectively retarded by combinations of 2 µg/g β‐carotene and 1.5 µg/g γ‐ or α‐tocopherol. The combination of β‐carotene and α‐tocopherol was significantly better in retarding oxidation than α‐tocopherol alone. While γ‐tocopherol was an effective antioxidant, a synergistic effect between β‐carotene and γ‐tocopherol could not be shown. The results indicate that there is a need to protect β‐carotene from oxidative destruction by employing antioxidants, such as α‐ and γ‐tocopherol, should β‐carotene be used in fat emulsions.