## 3 Detection of EVOO and VOO Adulteration by Gas Chromatography
This is important because levels of filbertone in this type of oil are lower than those derived from roasted hazelnuts oils [63]. [PERSON] et al. (2008) [48], using SPME/gas chromatography combined with mass spectrometry (GC-MS) and PCA, showed that gas chromatography could detect adulteration of an EVOO with hazelnut oil at 5% (v/v). Chemically, the volatile profile of these two oils is different. For example, EVOO is characterized by a high level of aldehydes (68%), whereas in olive oil of minor quality, the respective percentage is lower (38%), while ketones and acids constitute the majority. In this study, compounds that belong to the aldehydes family, as well as other compounds, helped distinguish EVOO from hazelnut oil, and these include E-2-hexenal, hexanal, pentanal, acetic acid, 2-octanone and 2-heptanone. Furthermore, many compounds such as propanoic acid, toluene and butanoate acid are present only in hazelnut oil. Consequently, based on quantitative and qualitative differences of the chemical profile between EVOO and hazelnut oil and by using chemometrics, adulteration can be detected. Volatile Profile of EVOO and VOO as an Index for Evaluating Its Authenticity by Gas Chromatography Based on Geographical Origin  
Olive oil volatile profile was studied by [PERSON] et al. (2004) [49], who aimed at distinguishing between EVOOs of different geographical origins. They used headspace (HS)-SPME followed by gas chromatography-ion trap mass spectrometry (GC-ITMS) combined \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Authors** & **Method** & **Collection of Volatiles** & **SPME Fiber Type** & **Focus** & **Chemometrics** \\  & & **(e.T.; i.e.) * & & & \\ \hline \multicolumn{6}{c}{**Discrimination According to Variety/Botanical Origin**} \\ \hline
[56] & GCMS-SPME & 2 h & DVB/CAR/PDMS & Differentiation of Turkish EVOOs & PCA analysis \\  & & 30 min & varieties & \\
[57] & HS-SPME- & 50 °C & & \\ GC/MS & 5 min & DVB/CAR/PDMS & Cultivar differentiation of Greek & MANOVA/LDA \\  & GC-FID & 15 min & olive oil & analysis \\  & HS-SPME- & 50 °C & & Virgin olive oil differentiation & ANOVA, PCA and \\
[58] & GC \(\times\) & 6 min & DVB/CAR/PDMS & according to variety and & SLDA analysis \\  & GC-TOF-MS & 40 min & & geographical origin & \\  & 10-GC-MS & 50 °C & & Comparison of Algerian virgin & \\
[59] & HS-SPME/CC- & 60 min & DVB/CAR/PDMS & olive oil in terms of variety and & - \\  & MS & 90 min & & geographical origin & \\
[60] & HS-SPME, & 25 °C & & Geographical and varietal & \\  & GC-MS & - & DVB/CAR/PDMS & discrimination of EVOO based on & - \\  & GC-MS & 50 min & & monoterene and sesquiterpene & \\  & & & hydrocarbons profile & \\  & & 40 °C & & Characterization of VOO varieties & \\
[61] & DHS-GC & - & - & according to quantification of & SLDA analysis \\  & & 15 min (sweep with N2) & & volatiles & \\
[9] & SPME-GC-MS & - & DVB/CAR/PDMS & Tracylylylverols and volatiles of & \\  & & 15 min & & EVOOs different varieties & \\
[62] & HS-SPME- & 50 °C & & \\  & GC/MS & 5 min & DVB/CAR/PDMS & Cultivar and geographical & ANOVA analysis \\  & GC-MS & 15 min & & classification of Greek olive oil & LDA \\
[44] & HS-SPME- & 50 °C & & \\ GC/MS & 30 min & DVB/CAR/PDMS & Botanical discrimination of Greek & stepwise LDA and \\  & GC-MS & 15 min & & EVOOs & QDA models \\ \hline \hline \end{tabular}
* e.T.: extraction temperature; i.t. incubation time; e.t. extraction time.  
\end{table} 
Table 2: \(Cont.\)with PCA, LDA and an artificial neural network with multilayer perception (ANN-MLP). The authors tested various types of fibers for their efficacy; however, they concluded that the most suitable was the DVB/CAR/PDMS (50/30 \(\upmu\)m) fiber. Samples were analyzed with the GC-ITMS technique, yet authors proposed that for those compounds where GC chromatographs were not clear, Two-Dimensional Gas Chromatography and Time-of-Flight Mass Spectrometry (GCXGC-TOFMS) was the adequate analysis to perform. Indeed, spectra quality was significantly improved.