Article

Journal of the American Oil Chemists' Society

, Volume 76, Issue 6, pp 749-755

Antioxidant activities of α- and γ-tocopherols in the oxidation of rapeseed oil triacylglycerols

  • Anna-Maija LampiAffiliated withDepartment of Applied Chemistry and Microbiology, Viikki-D, University of Helsinki Email author 
  • , Leena KatajaAffiliated withDepartment of Food Science, Swedish University of Agricultural Sciences (SLU)
  • , Afaf Kamal-EldinAffiliated withDepartment of Food Science, Swedish University of Agricultural Sciences (SLU)
  • , Piironen VienoAffiliated withDepartment of Applied Chemistry and Microbiology, Viikki-D, University of Helsinki

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Abstract

Antioxidant properties of 5 to 500 µg/g levels of α-and γ-tocopherols, in the oxidation of rapeseed oil triacylglycerols (RO TAG), were studied at 40°C in the dark. Each tocopherol alone and in a mixture was studied for its stability in oxidizing RO TAG. Also the effects of tocopherols on the formation of primary and secondary oxidation products of RO TAG were investigated. Both tocopherols significantly retarded the oxidation of RO TAG. At low levels (≤50 µg/g), α-tocopherol was more stable and was a more effective antioxidant than γ-tocopherol. At higher α-tocopherol levels (>100 µg/g), there was a relative increase in hydroperoxide formation parallel to consumption of α-tocopherol, which was not found with γ-tocopherol. Therefore, γ-tocopherol was a more effective antioxidant than α-tocopherol at levels above 100 µg/g. As long as there were tocopherols present, the hydroperoxides were quite stable and no volatile aldehydes were formed. In a mixture, α-tocopherol protected γ-tocopherol from being oxidized at the addition levels of 5+5 and 10+10 µg/g but no synergism between the tocopherols was found. α-Tocopherol was less stable in the 500+500 µg/g mixture than when added alone to the RO TAG. No prooxidant activity of either tocopherol or their mixture was found.

Key Words

Antioxidant rapeseed oil triacylglycerols α-tocopherol γ-tocopherol