Table options 3.1. Changes in Raman spectra during oxidation Full-size image (12 K) Fig. 2. Regions of the most prominent changes in the Raman spectrum of sunflower oil during 9 h oxidation: (a) 900–1200 cm−1, (b) 1200–1350 cm−1, (c) 1600–1775 cm−1 and (d) 2800–3050 cm−1. Figure options The spectrum of virgin olive oil showed initially Ponatinib band located at 1525 cm−1 which can be assigned to the Cdouble bond; length as m-dashC stretching in highly conjugated systems, like carotenoids. These compounds are present in virgin olive oil but not in the refined oils. Carotenoids have antioxidant properties as radical scavengers and singlet oxygen quenchers in lipid oxidation (Yanishlieva et al., 1998). The antioxidative behaviour of carotenoids is closely related to its own oxidation and the loss of carotenoids could be clearly observed at the beginning of the heating period in the band at 1525 cm−1, which disappeared after 90 min. 3.1.1. Formation of secondary oxidation products