Relationship among malondialdehyde, TBA-reactive substances, and tocopherols in the oxidation of rapeseed oil

Relationship among malondialdehyde (MDA), 2-thiobarbituric acid (TBA)-reactive substances (TBA-RS), and tocopherols in the oxidation of rapeseed oil was investigated. MDA was determined by a new HPLC method with chemical derivatization. When the oil was heated at 170 degrees C, TBA-RS and MDA increased. The contents of TBA-RS were approximately 1.6 times higher than those of MDA. Correlation between the increase in formed MDA and the decrease in tocopherols was observed. When the oxidation of the oil was initiated using 2,2'-azobis-(2,4-dimethylvaleronitrile) at 40 degrees C, TBA-RS dramatically increased during the initial stage and reached plateau. Thereafter, little increase was observed. The relative ratio of MDA to TBA-RS was much lower in the reaction performed at 40 degrees C than that observed at 170 degrees C. These results indicated that the decrease of tocopherols was accompanied by the increase of MDA but TBA-RS did not correlate with the change of tocopherols.