Authentication of Virgin Olive Oil Based on Untargeted Metabolomics and Chemical Markers

Virgin extra olive oil as a high-value edible oil is a potential object of adulteration. Refined camellia oil (RCO) could be one of the most challenging potential adulterants of olive oil to detect due to its high similarity in the fatty acid composition. In this study, an untargeted metabolomics strategy based on data from ultra-performance liquid chromatography-electrospray ionization-quadrupole-time of flight (UPLC-ESI-qTOF) measurements combined with statistical methods was applied to identify the unauthorized addition of RCO to extra virgin olive oil (EVOO). Untargeted fingerprints of the olive oil and RCO could be classified into two groups via unsupervised principal component analysis (PCA) that shows the significant difference of the fingerprints of polar components extracted from olive oil and CAOs, respectively. Orthogonal partial least squares-discriminant analysis (OPLS-DA) and volcano plots were used to identify markers with significant difference between these two oils. The results show that 927 and 780 features (positive and negative ESI modes), respectively, were higher regulated in virgin extra olive oil, whereas 439 and 479 features, respectively, were higher regulated in RCO. From these features, 28 markers for olive oil and 7 markers for CAO were tentatively identified. Further adulteration experiments showed that virgin extra olive oil containing more than 15% RCO could be distinguished from the olive oil by this untargeted UPLC-ESI-qTOF measurement, followed by unsupervised PCA. Furthermore, camelliagenin A (519.3695/12.22, [M + FA - H]-) could still be detected when EVOOs were mixed with at least 5% CAO.