Detection of Olive Oil Adulteration with Corn Oil Based on the Phenolic Compounds Profile Obtained by UHPLC-MS/MS

Unrefined vegetable oils are an important source of bioactive compounds with beneficial effects on health. Therefore, confirming the biological identity of oils is important for ethical and economic reasons. In this study, a method was developed for discriminating vegetable oils based on the phenolic compounds profile obtained by ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS). It was found that extra virgin olive oil has a cinnamic acid content of 2.2 mg/kg (mean value), a much higher value compared to other oils (not detected—0.4 mg/kg), thus being a representative phenolic marker for this oil. From the phenolic compounds profile of different vegetable oils, it can be stated that extra virgin olive oil has a specific phenolic content. However, walnut, sunflower, and corn oils have some similarities regarding the phenolic compounds content (for instance, ellagic acid) and, therefore, these oils can be used as adulterants of extra virgin olive oil. Data analysis, including principal component analysis, hierarchical cluster analysis, and partial least-squares discriminant analysis, demonstrated the discrimination of olive oils from other vegetable oils. Data analysis also allowed the discrimination and classification of olive oil samples adulterated with corn oil when the percentage of adulterant was 1%, with an accuracy of more than 90%.