Effect of Canolol (4-vinylsyringol) on the Oxidation of Edible Oils

Rapeseed contains high amounts of phenolic compounds, mainly derivatives of sinapic acid, but only a small part can be found in virgin rapeseed oil, since the polar compounds remain in the press cake. A temperature treatment of the raw material results in the degradation of sinapic acid to 2,6dimethoxy-4-vinylphenol (vinylsyringol or canolol), which is described in literature as a very strong antioxidive component. This compound shows good oil solubility and passes over into the oil during pressing. In the present work canolol was measured together with the tocopherols by HPLC and detected by fluorescence detector. During the heat-treatment the content of tocopherols was not affected while the content of canolol continuously increased with simultaneous decrease of sinapic acid. Higher amounts of canolol in rapeseed oil strongly improved the oxidative stability of the oil in the Rancimat test at 120°C. Canolol showed a significant antioxidant effect in the ß-carotene-linoleic acid assay.