Correlation of structural characterization and viscosity measurements with total unsaturation: An effective method for controlling ozonation in the preparation of ozonated grape seed and sunflower oils

Ozonated oils have demonstrated promising results for clinical applications. The reaction of ozone with the unsaturated compounds of oils produces by-products such as ozonides and poly peroxides. A deeper knowledge of the dynamics of by-product formation is helpful in determining the required ozonation degree to obtain therapeutic effects. The aim of this paper is to show the relationship between ozonation degree and structural and viscosity changes during the ozonation of grape seed (GS) and sunflower (SF) oils. Structural characterization was done by Fourier transform infrared (FT-IR) and hydrogen-1 nuclear magnetic resonance (¹H NMR) spectroscopy, with iso-ozonides being identified. Viscosity showed a significant increase during ozonation, a fact associated with poly peroxide formation. We have made use of the total unsaturation (TU) method to measure the ozonation degree. The TU of non-ozonated GS oil was found to be higher than for SF oil (5.94 and 4.49mmol per g of oil, respectively), and their by-product distributions were also found to differ. In GS oil, three reaction steps were observed for double-bond conversion into iso-ozonides and poly peroxides, while the ozonides and poly peroxides were formed in parallel in SF oil. The studies we implemented characterized the differences in the reactivities of these oils with ozone.