## 3 Results and Discussion
### Volatile Compound Profile of Hop Extracts Obtained under Different SFE-CO\({}_{2}\) Conditions

Table 8: _Cont._  
Sesquiterpenes represented the major fraction of volatiles, accounting for 33.8-38.7% of the total quantified by GC volatiles. Sesquiterpene hydrocarbons such as \(\beta\)-humulene (6.3-7.0%), \(\alpha\)-humulene (7.2-9.9%) and \(\alpha\)-selinene (5.5-14.9%) with intense woody, spicy and pepper-like notes were found at the highest percentages in the headspace of extracts absorbed by SPME. These compounds were followed by herbal \(\beta\)-selinene (3.9-4.6%) and \(\delta\)-calinene (1.5-4.7%) and fruity \(\alpha\)-ylangene (3.1-4.0%). Other identified sesquiterpene hydrocarbons individually contributed to less than 2% of the total GC peak area (Table 5). [PERSON] and coworkers recently reported a high share of humulene, seliene and cadinene in the overall sesquiterpene content (43%) for the _Ella_ hop essential oil obtained by hydrodistillation [26]. Both the percentage content (Table 5) and peak areas (Supplementary Materials, Table S4) indicate that sesquiterpene profile was dependent on extraction parameters, particularly P. For example, \(\alpha\)-selinene significantly reduced from 14.9% (or \(182\times 10^{7}\) AU) at 10 MPa to 5.5% (or 49 \(\times\) 10\({}^{7}\) AU) at 37 MPa. The extracts obtained at 10 and 12.5 MPa generated higher peak areas and percentage content of \(\alpha\)-humulene (90-121 \(\times\) 10\({}^{7}\) AU; on average, 9.8%) than at 15 and 37 MPa (67-72 \(\times\) 10\({}^{7}\) AU; on average, 7.6%). The share of \(\beta\)-humulene in the headspace remained relatively stable, amounting to \(\sim\)6.6% of the total GC peak area across the different extracts tested with no significant differences in AU at P \(>\) 12.5 MPa. Only negligible amounts (<0.5%) of oxygenated sesquiterpene carcyophyllene oxide were found in extracts obtained up to 15 MPa (Table 5), while humulene epoxide II, previously reported in _Ella_ hop essential oil at 0.4% [26], was not detected in these experiments. The percentage of monoterpenes in the headspace increased from 10.5% (or 127 \(\times\) 10\({}^{7}\) AU) to 17.6% (or 154 \(\times\) 10\({}^{7}\) AU) when P was raised from 10 to 37 MPa (Table 5; Supplementary Materials, Table S4). These changes were obtained due to the \(\sim\)2-fold higher peak areas of herbal \(\beta\)-pinene (63 \(\times\) 10\({}^{7}\) AU; 7.0%) and spicy \(\beta\)-myrrene (56 \(\times\) 10\({}^{7}\) AU; 6.2%) at 37 MPa as compared to 10-15 MPa, both being the major identified monoterpene hydrocarbons. Linalool with the distinctively floral, citrus, woody and green notes was the only identified oxygenated monoterpene in _Ella_ hop SFE-CO\({}_{2}\) extracts. Its content did not significantly change at P \(>\) 12.5 MPa, \(\sim\)2.0% of the total GC peak area equivalent to \(\sim\)19 \(\times\) 10\({}^{7}\) AU across different extracts tested. As reported by [PERSON] et al., both myrrene and linalool are aromactive constituents with the highest flavor dilution factor values among the other hop volatiles [29]. Recently, [PERSON] et al. suggested that the ratio of \(\alpha\)-humulene/\(\beta\)-myrrene could be used as one of the parameters to differentiate between the aroma, bittering and dual-purpose hops [44]. For _Ella_ hop SFE-CO\({}_{2}\) extracts this ratio gradually decreased from 3.3/1 at 10 MPa to 2.5/1 at 12.5 MPa, 1.9/1 at 15 MPa and 1.3 at 37 MPa (Table 5; Supplementary Materials, Table S4), suggesting that P increase can shift the aroma profile of extracts from the dual-purpose hop typical characteristics towards the bitter hop-related ones [44]. The tunability of SFE-CO\({}_{2}\) parameters to produce hop extracts with the desired organoleptic properties was previously demonstrated by [PERSON] et al. as well [13; 14]. Esters accounted for 12.2-22.3% of the identified headspace volatiles, with higher peak areas (Supplementary Materials, Table S4) and percentages (Table 4), thus more pronounced fruity, green and floral notes at P \(>\) 10 MPa.