Aroma profiles of vegetable oils varying in fatty acid composition vs. concentrations of primary and secondary lipid oxidation products

The aroma compositions of oxidised sunflower oil, linseed oil and a blend thereof (85/15) were compared with frequently used indicators for primary and secondary lipid oxidation. Primary lipid oxidation was followed by the formation of conjugated dienes, secondary lipid oxidation by proponal and hexanal formation. Highest concentrations of conjugated dienes and propanal were measured in the linseed oil, followed by the blend and sunflower oil, respectively. Highest concentrations of hexanal were determined in the blend. At similar primary oxidation levels, volatile compounds of the oils were isolated in a model mouth system and subsequently analysed by gas chromatography/sniffing port analysis. Propanal, pentanal, 1-penten-3-one, hexanal, 1-pentanol, octanal, 1-octen-3-one, 1-octen-3-ol and (E,Z)-2,4-heptadienal possessed detectable odours. Comparing the three oils, most aroma compounds and greatest intensities were determined in the blend. Conjugated diene concentrations did not predict the formation of aroma compounds adequately. Although propanal and hexanal concentrations were reasonable indicators for aroma development in linseed and sunflower oil, respectively, neither of the indicators predicted aroma development in all three oils sufficiently.