Antioxidative activity of 3,4-dihydroxyphenylacetic acid and α-tocopherol on the triglyceride matrix of olive oil. Effect of acidity

Abstract

Minor constituents of virgin olive oil are important for the remarkable stability of the oil in autoxidation, but the exact role and the extent to which each antioxidant factor contributes to the total antioxidant effect has not been thoroughly investigated. In this study the role of α-tocopherol is explored at various acidity levels and at low concentrations of ortho-diphenols. A substrate of olive oil triacylglycerols devoid of prooxidant or antioxidant constituents was prepared from refined olive oil by column chromatography. To this substrate, slightly oxidized, the additives (oleic acid, 3,4-dihydroxyphenylacetic acid and α-tocopherol) were added and the stability was assessed by periodical measurements of peroxide values. It was found that free fatty acids reduce mainly the protective activity of the ortho-diphenol. It is also concluded that α-tocopherol has a synergistic effect with the ortho-diphenols and contributes significantly to the retardation of peroxide formation. This is important for oils poor in ortho-diphenols.