## 3 Results and Discussion
### Identification of Volatile Metabolites in Analyzed Grape Marc Spirits
Anethol was found in very high concentration in Limnos samples, followed by aniseed Muscat samples from Macedonia, while estragole, menthol, 4-anisaldehyde, \(p\)-anisaldehyde diethyl acetal, _alpha_-himachalene, _gamma_-himalachene, and aromadendrene, which were the main flavored compounds detected in aromatized Greek tispuoro, were found mostly in Limnos samples (Figure 3). Most of them have also been identified in Turkish raki, Greek and Cypriot ouzo, and other European distillates [29; 50]. Aromatic terpen, such as _alpha_-himachalene, _gamma_-himalachene, _alpha_-cadinene, and _alpha_-curcumene, have been previously identified in essential oils and aromatized distillates from Turkey, and their presence in Greek tispuoro arises from the addition of aromatic material during distillation [29; 48; 51]. 3-Acetylphenol, fenchone, carvone [52], and estragole were found in higher concentrations in Thess  
Figure 2: Boxplots of representative terpenols among Greek grape marc spirit samples. Black dots represent the samples’ values and yellow dots are the mean values. while _gamma_-isogenariol, _trans-p_-mentha-1(7),8-dien-2-ol and thymyl ethyl ether were more abundant in Thessaly samples, as illustrated in Figure 4.  
According to [PERSON] et al. [53], a group of volatile compounds that has a strong contribution to fruity and flowery aromas of distillates is ethyl esters. Their concentration is influenced by grape variety, but they are formed during the alcoholic fermentation of grape marc [25]. During the aging of distillates, the concentration of hexanoate, octanoate, and decanoate ethyl esters increases, reaching higher levels than that of their corresponding fatty acids. These ethyl esters were found to be more abundant in Macedonia, Thessaloniki, and Pella samples, while ethyl palmitate was higher in Limmos and Thessaloniki samples, as is shown in Figure S1, which are produced mainly from Muscat grapes, with the addition of anise, and red multi-variety grapes. Ethyl lactate is another important ester in grape pomace spirits, since it is considered to stabilize the spirit flavor and soften the harsh flavor characteristics [10]. Its presence in spirits in high concentrations, is linked to the pomace's malolactic fermentation by lactic bacteria, and the production of lactic acid by malic acid. Hence, the low concentration of this compound in the majority of the analyzed samples is indicative of the quality of the raw material and therefore the resulting distillate. These concentration levels are much lower than those of grappas and orujos found by [PERSON] et al. [25; 30]. Ethyl acetate is often the most abundant ester of spirits, with an important contribution to the organoleptic characteristics of distilled alcoholic beverages, while concentration levels of 150-200 mg L\({}^{-1}\) can add spoilage notes to the wine, having \"fingernail polish remover\" properties [9; 26; 54]. The concentration of ethyl acetate in this study was found to be in low levels in most of the samples, which may contribute to the floral and fruity properties of the grape marc spirit. However, its concentration exceeded the aforementioned level in the distillates of Macedonia and Thessaly. Similar levels of ethyl acetate were detected by [PERSON] et al. [10] in Greek bottled and homemade  
Figure 3: Boxplots of representative flavored compounds resulting from the addition of anise in Limnos tispouro samples. Black dots represent the samples’ values and yellow dots are the mean values. acetate has also been detected in spirits in low concentrations. High concentration levels of these acetate esters are important indicators of aerobic fermentation and storage conditions, or an incorrect separation distillation fraction [9; 30]. Isoamyl and phenethyl acetate were detected in all analyzed samples, contributing flowery and fruity notes to the beverages, but in lower concentrations than in traditional and industrial orujos samples [25].