## 4 Discussion
On the other hand, it was found to have high amounts of hexanal, particular C6 alcohols, and hexyl acetate, compounds often accounted among the carriers of _green_ odor which derive from the enzymatic degradation of linoleic acid but also oxidation [10; 28; 55]. Lastovka EVOO contained the highest concentrations of particular monoterpenes and sesquiterpenes, whose sensory contribution is generally described by descriptors such as _citrus_, _camphor_, _eucalyptus_, _roses_, etc., as well as _wood_. Although sensory relevance of terpen in olive oil is currently still unknown and it is certainly limited by the lipid matrix in which these lipophilic molecules are highly soluble, the possibility of their contribution to the specific _wood_ odor perceived in Lastovka EVOO during sensory analysis (Figure 3, Table S3) should not be excluded. Several terpen were extracted by PLSDA as among the most discriminative compounds for this variety (Figure 2). Particular sesquiterpenes, on the other hand, such as (+)-cycloisosavitene, \(\alpha\)-copaene, \(\alpha\)-muuroclone, \(\delta\)-cadinene, and several unidentified ones were found in the lowest concentrations in Lastovka EVOO (Table 1). Terpenes were previously found to have large potential to differentiate EVOO according to variety [16; 56], which was basically confirmed in this study. Other compounds found to be characteristic for Lastovka EVOO, such as particular saturated short-chain aldehydes, ketones, alcohols, and acids, could also have had a sensory impact with their _malty_, _pungent_, _rancid_, and _sweaty_ nuances (Table 2). One of probably the most important characteristics found typical for Leccino EVOO was the ratio between the important (_E_)-2- and (_Z_)-3-C6 forms, which was generally the highest and discriminated well this EVOO from the majority of the other studied EVOOs (Tables 1 and 2). The highest concentration of (_E_)-2-hexenal and the lowest concentration of (_Z_)-3-hexenal, (_Z_)-3-hexen-1-ol, as well as the low concentration of (_Z_)-3-hexenyl acetate in Leccino EVOO were likely the result of high (_Z_)-3:(_E_)-2-renal isomerase activity in Leccino olives, i.e., olive paste during milling and malaxation steps [57]. Considering that the estimated contribution of (_E_)-2-hexenal to the aroma of EVOOs was generally lower than that of (_Z_)-3-hexenal (Table 2), it is possible that one of the consequences of the observed differences was a slightly lower intensity of particular odor sensory attributes, such as _green/grass leaves_ and _chicory/rocket_, observed in Leccino with respect to the EVOOs from the other, native Istrian varieties Buza, I. bijelica and Rosinjola (Figure 3, Table S3). Other interesting features of Leccino EVOO included lower concentrations of particular sesquiterpenes and furanoids. In fact, many sesquiterpenes were among those with the highest VIP scores extracted by PLSDA, but with a negative sign (Figure 2). Phenols, especially secoiridoids, are responsible for the characteristic EVOO bitterness and pungency, but the specific sensory contribution of each individual major secoiridoid has not been precisely elucidated up to date. Nevertheless, there is solid evidence that _p_-HPEA-EDA is a key contributor to pungency, while the pungency of other, monoaldehyde ligstroside aglycons is weaker, although still strong [24]. Ligstroside aglycons were found to generally be less bitter than pungent, which was especially the case for _p_-HPEA-EDA. In the same study [24] it was found that the majority of oleuropein aglycons, including 3,4-DHPEA-EDA, was described as both bitter and pungent, with some of them exhibiting rather strong bitterness. The lowest intensity of bitterness observed in Oblica and Leccino (Figure 2, Table S3) could be tentatively linked to the lowest oleuropein aglycon I concentrations found in these EVOO (Table 3). The intensity of pungency did not quite correlate with the average \(p\)-HPEA-EDA concentrations (Figure 3, Table 3, Table S3).