High power ultrasound effects on lipid oxidation of refined sunflower oil.

The effects of high power ultrasound treatment (20 kHz) on some components of refined sunflower oil were studied in order to verify if and to what extent modifications in the lipidic fraction can occur. Traditional parameters including free acidity, total polar compounds, peroxide value, and conjugated dienes concentration were determined in refined sunflower oil samples before, immediately after the ultrasonic treatment and during storage. Differences between treated and untreated samples were detected only for peroxide values (PV). The PV increased from 5.38 meq. O2/kg oil for untreated oil to 6.33 meq. O2/kg oil for sunflower oil sonicated (20 kHz; 150 W; 2 min). The fatty acid composition was obtained by high resolution gas chromatography. No significant changes were observed regarding the decrease in fatty acid composition before and immediately after the treatment. Regarding the volatile fraction, some off-flavour compounds for example hexanal and limonene resulting from the ultrasonic degradation of sunflower oil were identified by gas chromatography coupled to mass spectrometry (GC-MS).