## 3 Results and Discussion
### Volatile Composition of Olive Oil
The highest and lowest content of ketones (\(p\) < 0.05) was observed in the LES (22.4%) and CRE (12.3%) samples, respectively, whereas the LES samples displayed a lower value of esters (11.9%, \(p\) < 0.05) in comparison with samples from the other regions. Significant differences were also found in the minor chemical classes. Specifically, the acid content ranged from 4.3% to 6.5% (PEL and LES, respectively; \(p\) < 0.05). As far as hydrocarbons and terpenoids are concerned, the CRE samples displayed higher content (\(p\) < 0.05) than the samples from the other regions (8.7% for hydrocarbons and 4.0% for terpenoids), while the lowest content was observed in samples from LES (6.1% for hydrocarbons and 0.8% for terpenoids). When the samples were studied according to their cultivar (Figure 2), the content of alcohols varied from 43% to 50%, ketones from 14% to 24%, esters from 12% to 18% and aldehydes between 4% and 11%. ADR and KOR cultivars differed significantly due to their alcohol content (49.5% and 41.9%, respectively; \(p\) < 0.05), with samples from ADR cultivar displaying higher levels. The highest and lowest content of ketones (\(p\) < 0.05) was observed in the KOL (23.5%) and KOR (14.4%) samples. On the contrary, the highest value of aldehyde content was evident in the KOR samples (11.5%) and the lowest value in the ADR samples (3.8%, \(p\) < 0.05). The KOR samples displayed a higher content of esters (17.8, \(p\) < 0.05), whereas the samples of KOL and ADR presented similar levels (12.0% and 11.8%). The same pattern was observed for terpenoids (KOL: 0.73%, ADR: 1.1% and KOR: 2.7%). The ADR samples displayed a much higher content of acids (\(p\) < 0.05) than KOL and KOR (12.4%, 5.16% and 5.0%, respectively) and the lowest content of hydrocarbons (4.13%, \(p\) < 0.05). Similar studies regarding EVOO classification of Greek cultivars from various regions have shown that the most prominent volatile compounds are C6 aldehydes and alcohols, deriving from the LOX pathway [12], which was also confirmed in the present study. Figure 2: Comparison of the relative content (%) of the chemical classes of volatile compounds identified in EVOOs originated from various cultivars. KOL: Kolovi; ADR: Adramytini; KOR: Koroneiki. The error bars indicate standard errors at 95% confidence level. Data in the same class with different lowercase letters differ significantly (\(p\) < 0.05). [PERSON] et al. [24] studied olive oil samples belonging to the Koroneiki cultivar from regions of the Peloponnese (Messenia and Lakonia) and Crete (Heraklion). In accordance with our results, they reported that the alcohol content of the samples from Crete was slightly lower than that of the samples from the Peloponnese and contained higher levels of hydrocarbons. However, an opposite trend than the one found in our study was reported for ketones and esters, which were present at slightly higher levels in Crete samples. [PERSON] et al. [5] also studied olive oil samples from various Greek regions and different cultivars, including Koroneiki and Adramytini. As in our study, aldehydes and esters were present at higher levels in the Koroneiki samples. On the contrary, alcohols and ketones were found in slightly higher levels in the Adramytini samples.