Abstract
The challenging process of high-quality food authentication takes advantage of highly informative chromatographic fingerprinting and its identitation potential. In this study, the unique chemical traits of the complex volatile fraction of extra-virgin olive oils from Italian production are captured by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry and explored by pattern recognition algorithms. The consistent realignment of untargeted and targeted features of over 73 samples, including oils obtained by different olive cultivars (n = 24), harvest years (n = 3), and processing technologies, provides a solid foundation for sample identification and discrimination based on production region (n = 6). Through a dedicated multivariate statistics workflow, identitation is achieved by two-level partial least-square (PLS) regression, which highlights region diagnostic patterns accounting between 58 and 82 of untargeted and targeted compounds, while sample classification is performed by sequential application of soft independent modeling for class analogy (SIMCA) models, one for each production region. Samples are correctly classified in five of the six single-class models, and quality parameters [i.e., sensitivity, specificity, precision, efficiency, and area under the receiver operating characteristic curve (AUC)] are equal to 1.00.
Highlights
Olive oil (OO) is one of the pillars of the Mediterranean diet and represents the main source of fats in the countries of the Mediterranean basin.[1]
Extra-virgin olive oil (EVOO) is recognized as the most valuable product among the edible oils;[2] it is extracted from fresh olive fruits (Olea europeae L.) by mechanical or physical technologies that preserve the composition of the lipid fraction while limiting autoxidation reactions and alterations of its native quality.[3]
Any analytical methodology capable of delineating chemical patterns informative of the different functional variables influencing the composition of extra-virgin olive oil (EVOO) is useful and has the potential to support the valorization of highquality products, facilitate sensory quality evaluation/screenings on the basis of commercial classification, as well as to counteract fraudulent practices.[4−7] In this latter context, the accurate fingerprinting of the unsaponifiable fraction and of minor components by comprehensive two-dimensional (2D) gas chromatography coupled to mass spectrometry
Summary
Olive oil (OO) is one of the pillars of the Mediterranean diet and represents the main source of fats in the countries of the Mediterranean basin.[1]. The amount of sample was chosen matching for HS linearity conditions for most of the characteristic analytes of the EVOO volatile fraction.[21,24,25] After extraction, the SPME device was automatically transferred to the split/splitless injection port of the GC × GC system kept at 250 °C, and thermal desorption was for 5 min. The approach, named UT fingerprinting, was designed on EVOO volatile patterns and further adapted to compositional peculiarities of samples in other fields.[11] In this study, the targeting (i.e., identification) of analytes was done as the last step of the process after chromatogram realignment over reliable peaks from untargeted components/features. Standard Deviation (% RSD) Calculated over Six Analytical Replicates over 2 Weeks and Referred to Retention Times and 2D Peak Volumes; Experimental 1D IT and Tabulated IT Values; Identification Criteria (a) Reference Compound Confirmation or (b) Spectral Direct Match Similarity and IT ± 20 Tentative Identificationa chemical class alcohols esters lactones fatty acids compound name
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