Headspace-solid-phase microextraction-gas chromatography was used to identify in total 55 volatile lipid oxidation compounds in thermally stressed conventional and high-oleic rapeseed oil samples. Out of this profile, 17 volatile compounds with low odor threshold values were selected as target compounds for the assessment of lipid oxidation in rapeseed and high-oleic rapeseed oils. Additionally, other lipid oxidation parameters such as fatty acid composition, peroxide value, anisidine value, and induction time (Rancimat analysis) were determined. Multivariate statistical methods (principal component analysis in combination with agglomerative hierarchical cluster analysis) were applied to identify sensitive volatile lipid oxidation indicators enabling the differentiation of rapeseed oil samples of different varieties (high-oleic versus conventional). Moreover, these statistical methods were capable of differentiating rapeseed oils of different oxidative properties. Octanal and 3-octanone showed the highest ability to differentiate between samples of different rapeseed varieties, whereas propanal, E,E-2,4-hexadienal, and E-2-heptenal were most suitable in differentiating rapeseed oil samples with different oxidative properties from each other. Clustering of rapeseed oil samples according to their volatile compound composition was comparable with results of sensory duo-trio and paired comparison tests, but the analytical approach of the volatile compound analysis in combination with chemometric methods detected changes sooner in relation to the flavor composition of rapeseed oils and high-oleic rapeseed oil samples.
Practical applications: The combination of volatile compound analysis by HS-SPME-GC with multivariate statistical methods and complementary sensory duo-trio and one-sided paired comparison tests are sensitive tools in differentiating conventional and high-oleic rapeseed oil samples with different lipid oxidation properties. The presented methods are suitable techniques for the detection of initial changes of lipid oxidation progress in edible oils.