## 2 Results and Discussion
### Aromatic Profile Analysis
The different winemaking technologies significantly (_p_ < 0.001) influenced the concentration of esters in the wines. The concentration of esters in the Muscat Hamburg wine made by carbonic maceration was higher than that in the Muscat Hamburg wine made by classical white and red-winemaking techniques. This result was attributed to a much higher content of ethyl esters (ethyl octanoate, ethyl hexanoate and ethyl decanoate) and acetate esters (hexenyl acetate, isoamyl acetate and phenylethyl acetate). Ethyl esters, which are derived from medium-chain fatty acids, are responsible for the fruity character of wines, the most representative aroma family in all wines. Ethyl octanoate, ethyl hexanoate and ethyl decanoate, which are associated with pleasant notes \"pear\", \"banana\" and \"fruity\", were the most abundant ethyl esters. Acetate esters, which are formed from acetic acid and higher alcohols, have a greater influence on the perceived aroma than ethyl esters [21]. Among the quantified acetate esters, three compounds (hexenyl acetate, isoamyl acetate and phenylethyl acetate) were associated with the positive attributes \"fruits\", \"banana\" and \"floral\" in the Muscat Hamburg wines. The contents of ethyl esters and acetate esters were significantly higher (_p_ < 0.001) in the Muscat Hamburg wine made by carbonic maceration. In addition, our results, which indicate higher levels of ethyl octanoate, ethyl hexanoate and ethyl decanoate in the Muscat Hamburg wines, are consistent with the results of previous studies on Muscat wines [22]. The concentrations of terpenes in the wines ranged from 405.1 to 787.9 ug/L. (\(\pm\))-\(\beta\)-Citronellol, linalool and limonene were the greatest contributors to the higher concentration of terpenes in Muscat Hamburg wine. Similar results were observed in a previous study that reported that aromatic varieties, such as Muscat Hamburg, Gewurztraminer, Irsai Oliver and Rhine Riesling, had the highest terpenoid concentrations [23]. In addition, the contents of terpenes were significantly (_p_ < 0.001) higher in the wine produced by carbonic maceration (787.9 ug/L) compared with the levels in the wines produced by white- and red-winemaking techniques (678.96 ug/L and 405.1 ug/L, respectively). This result agrees with the previous finding that both the free and bound terpenoid contents were markedly higher when using carbonic maceration at higher temperatures (32 \({}^{\circ}\)C) [24]. These terpenes played a key role in the OAVs of Muscat Hamburg wines due to the low thresholds of these terpene compounds, such as (\(\pm\))-\(\beta\)-citronellol, linalool and limonene. Numerous studies have reported that terpene compounds can be used analytically for varietal characterization. Terpene compounds are secondary plant metabolites derived from acetyl Co-A. Terpenes are also synthesized by microorganisms; however, the synthesis of terpenes by _Saccharomyces cerevisiae_ has not been observed. Terpenes are important components of varietal aroma and are not influenced by yeast metabolism during fermentation [25]. Low numbers of aldehydes (four), ketones (one), acids (two) and alcohols (two) were detected in the Muscat Hamburg wines, and their concentrations were much lower than those of the other aroma compounds. Due to its low odor threshold (0.05 ug/L), \(\beta\)-damascenone contributed substantially to the OAVs. Alcohols are formed by the degradation of amino acids, carbohydrates and lipids [26]. The production of fatty acids has been reported to be dependent on the composition of the must and the fermentation conditions [27]. Fatty acids are associated with fatty olfactory notes [20]. Among the 32 volatile compounds identified and quantified in the wines, only 17 compounds were detected at levels above their odor thresholds (OAVs > 1), and these compounds included an alcohol, an aldehyde, a ketone, terpenes (five) and esters (nine). Ethyl octanoate had the highest OAV (> 300), followed by \(\beta\)-damascenone (OAV > 100) and then (\(-\))-rose oxide.