## 3 Results and Discussions
### Aroma-Active Compounds (AACs) of the Mastic Gum Samples  
The AACs identified in the mastic gum samples, their associated odors, and flavor dilution (FD) values are provided in Table 3. The analysis revealed 10 and 17 AACs in the MGT and MGG samples, respectively, indicating a greater number of AACs in the MGG sample. The variation in the number of the AACs of the two samples is likely due to regional differences such as climate and soil composition, which highlights the significant influence of geographical factors on the AACs. The sensory analysis results obtained in the present study aligned with this observation, as the panelists described the odor of the MGG sample as more intense and resinous. To the best knowledge of the authors of the present article, only one study in the literature examined the characteristic odors of mastic resins using GC-MS-O [11]. As can be seen in Table 3, the MGT sample contained five monoterpens, two monoterpens, one volatile phenol, one volatile acid, and one unknown compound (LRI: 1480), which could not be identified via GC-MS due to the peaks being too small and/or the mass/charge (\(m/z\)) ratios not being available in the MS library. On the other hand, the MGG sample included eight monoterpens, four monoterpens, one sesquiterpene, one alcohol, one volatile phenol, one volatile acid, and one aldehyde. The most active AAC in the MGT and MGG samples was identified as \(\alpha\)-pinene (a monoterpene), with FD values of 256 and 512, respectively. This compound contributed resinous and forest-like odors to the samples. Similarly, in a previous study that identified the AACs in mastic gums obtained from Greece's Chios Island using two different aroma extraction techniques (Headspace Solid-Phase Microextraction (HS-SPME) and Headspace Sportive Extraction (HS-SBSE)), \(\alpha\)-pinene was found to be one of the most dominant AACs, imparting forest-like and resinous odors (with FD values of 256 and 128, respectively) [11]. Furthermore, \(\alpha\)-pinene was also identified as an AAC in frankincense (_Boswellia sacra Flueck._) in a prior study [37]. In the MGT sample, the most abundant AACs after \(\alpha\)-pinene were identified as \(\beta\)-pinene (FD: 128) and \(\beta\)-myrcene (FD: 256), both being monoterpene compounds, along with linalool (FD: 256), a monoterpenoid compound (Table 3). These constituents were found to impart resinous, terpene-like; pine-like, greenish; and floral, fruity odors, respectively. Similarly, in the MGG sample, the most dominant AACs after \(\alpha\)-pinene were \(\beta\)-myrcene (FD: 128), \(\beta\)-pinene (FD: 128), and linalool (FD: 128), respectively. The \(\beta\)-pinene compound has been identified before in various products, including mastic gums [11] and the fresh and roasted fruits of another _Pistacia_ species, _P. terbehintus_[38], contributing resinous, piney, and terpene-like notes. \(\beta\)-Myrcene was identified in frankincense as an AAC [37], while linalool was associated with floral and sweet notes in previous studies [39]. Limonene, a monoterpene compound, was determined as an AAC in the current study (Table 3) with FD values of 32 and 16 in the MGT and MGG samples, respectively, giving a citrus, fruity odor to the samples. Similarly, it was detected in the mastic gum sample obtained from Chios Island of Greece by [PERSON] et al. [11] and in frankincense gum by [PERSON] and [PERSON] [37]. Limonene is responsible for the characteristic aroma of many citrus fruits such as orange, tangerine, and lemon and it was also detected as the AAC in lemon juice [40] and bergamot essential oil [41]. Another monoterpene, perillene, was determined with FD values of 16 and 64 in the MGT and MGG samples, respectively, providing greenish, pea-likeodors to the mastic gum samples. In the study conducted by [PERSON] et al. [11], perillene was determined as one of the most dominant AACs in mastic gums.