The presence of conjugated dienes (CD), similarly to the peroxide value, is a parameter for the determination of the
oxidative stability of vegetable oils. It is evaluated by the absorbance at the wavelength of 232 nm. The formation
of hydroperoxides coincides with the conjugation of the double bonds in polyunsaturated fatty acids (PUFA).
The CD values of the samples during storage are displayed. It is observed that a gradual increase occurred in the
formation of conjugated dienes, in all the samples. Up to the 14 day, the samples of sunflower oil, corn oil, and
soybean oil, with the addition of rosemary extract and TBHQ showed low values of CD, differently to the other
samples. This occurs probably by the protecting effect of the antioxidants in inhibiting the formation of the primary
oxidation products. After the 21st day, a rapid rise in the CD values was observed for the samples without additives.
The CD values for the samples without additives, conversely to what was observed for the peroxides, revealed a
protection factor effect similar among the antioxidants, showing that the activity of an antioxidant cannot be
determined by only one parameter