## 3 Results and Discussions
### Aroma-Active Compounds (AACs) of the Mastic Gum Samples
In both MGT and MGG samples, one volatile phenol (2-methylanisole), one volatile acid (acetic acid), and one monoterenoid ((\(Z\))-verbenol) were identified as AACs (Table 3). The 2-methylanisole compound was found to impart woody, fresh odors to the mastic gums, also reported by [PERSON] et al. [11], who noted a woody aroma contribution in mastic gums. Additionally, this constituent was identified as an AAC in frankinense by [PERSON] and [PERSON] [37]. Acetic acid was found to contribute a vinegary odor to the samples, while (\(Z\))-verbenol was associated with a pine-like aroma in the present study. Similar findings were reported by [PERSON] et al. [11], where both acetic acid and (\(E\))-verbenol were identified as AACs in mastic gums. Furthermore, acetic acid has been reported as an AAC contributing to the odor in certain Citrus species [42]. In the MGG sample, unlike the MGT sample, three monoterenes (camphene, \(p\)-cymene, (\(E\))-verbenone), two monoterpencids (myrtrenal and perilla alcohol), one sesquiterpene (caryophyllene oxide), one alcohol (2-hexanol), and one aldehyde (\(\alpha\)-campolenal) were identified as AACs in the present study (Table 3). Among these, (\(E\))-verbenone, 2-hexanol, caryophyllene oxide, and perilla alcohol were identified as AACs in mastic gum for the first time. In an earlier study, compounds such as camphene (pungent, spicy, buttery), myrtrenal (sharp, sweet), and \(\alpha\)-campolenal (herbaceous, fresh) were also found to be AACs in the mastic gum samples, which is consistent with our findings [11]. \(p\)-Cymene and (\(E\))-verbenone were identified as AACs in frankinense in a prior study, imparting fruity and spicy odors, respectively [37]. Most of the compounds identified in the mastic gum samples have pine-like, resinous, and pungent notes in the present study (Table 3) and the combination of these constituents is responsible for the characteristic odor of the mastic gum samples. [PERSON] et al. [36] reported that the overall organoleptic quality of mastic essential oils is not dependent on a single aroma compound but is influenced by minor components in addition to the main \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**No**} & \multirow{2}{*}{**LRI 1**} & \multirow{2}{*}{**Compounds**} & \multirow{2}{*}{**Odor Descriptions**} & \multicolumn{2}{c}{**Flavor Dilution, FD 2**} \\ \cline{5-6}  & & & & **MGT** & **MGG** \\ \hline
1 & 1011 & \(\alpha\)-Pineine & Forest like, resinous & 256 & 512 \\
2 & 1057 & Camphene & Pungent, spicy, pine-like & nd & 2 \\
3 & 1096 & \(\beta\)-Pine & Resinous, terpene-like & 128 & 128 \\
4 & 1167 & \(\beta\)-Myrrene & Pine-like, greenish & 256 & 128 \\
5 & 1196 & Limonene & Citrus, fruity & 32 & 16 \\
6 & 1265 & \(p\)-Cymene & Citrus & nd & 2 \\
7 & 1226 & 2-Hexanol & Wine like & nd & 4 \\
8 & 1390 & 2-Methylanisole & Woody, fresh & 2 & 4 \\
9 & 1431 & Perillene & Greenish, pea like & 16 & 64 \\
10 & 1452 & Acetic acid & Vinegar like & 4 & 4 \\
11 & 1447 & \(\alpha\)-Campolenal & Grassy & nd & 4 \\
12 & 1497 & Linalool & Floral & 256 & 128 \\
13 & 1480 & Unknown & Earthly & 2 & nd \\
14 & 1648 & Myrtrenal & Spicy, pungent & nd & 16 \\
15 & 1669 & (\(E\))-Verbenol & Pine-like & 2 & 4 \\
16 & 1679 & (\(E\))-Verbenone & Camphorous & nd & 4 \\
17 & 1953 & Caryophyllene & Woody & nd & 4 \\
18 & 1985 & Perilla alcohol & Greenish & nd & 8 \\ \hline \hline \end{tabular} \({}^{\dagger}\)LRI: Linear retention index calculated on DB-WAX column. 2 Flavor dilution factor was determined by the aroma extract dilution analysis (AEDA); nd: not detected.  
\end{table} 
Table 3: The aroma-active compounds of the mastic gum samples from Türkiye (MGT) and Greece (MGG). constituents. However, they also noted that these components change with the harvesting of mastic gums, thereby affecting their characteristic odors.