## 3 Results and Discussion
### Quantification and OAV Analysis of Aroma Compounds
Higher concentrations and OAVs of esters in the pervaporation produced peach spirit explained why the intensity of fruity property was stronger in the pervaporation produced peach spirit than in the distilled peach spirit. As mentioned above, esters preferred to pass through organophilic membranes and be received into the permeate to make spirits, especially short-chain esters with high hydrophobicity, which contribute to fruity stents [37]. Alcohols are mainly generated during the fermentation process. After separation, the total concentration of alcohols in the pervaporation produced peach spirit was significantly higher than that in the distilled peach spirit. Although about 10 alcohols were identified, and 5 and 7 alcohols were quantified in the distilled peach spirit and pervaporation produced peach spirit, respectively, only 3 alcohols had OAVs greater than 1. 3-Methyl-1-butanol (malty and nail polish-like) and 1-hexanol (green) presented OAVs as 7 and 3 in the distilled peach spirit, and as 7 and 6 in the pervaporation produced peach spirit. While isobutanol was only quantified in the pervaporation spirit with the OAV as 22, contributing malty aroma property. Combined with FD factors, the aroma contribution of these three compounds needs attention and further research. Although there were significant differences in the concentrations and OAVs of alcohols in the distilled peach spirit and pervaporation produced peach spirit, the intensities of malty and grass in the two peach spirits had no difference. The reason might be the perceptual interaction of alcohols with other aroma ingredients in a complex matrix environment [38]. Lactones were characteristic aroma compounds of peach and peach wine, contributing to peach and apricot odor. Lactones were mainly concentrated in the pervaporation produced peach spirit. A total of 4 lactones were quantified. Among them, although the FD factor of \(\gamma\)-butyrolactone was low, it was the most abundant lactone in both peach spirits, presenting a fruity aroma, and its content in pervaporation produced peach spirit was 5 times higher than in distilled peach spirit. \(\gamma\)-Decalactone with high FD factor had an OAV as 5 in pervaporation produced peach spirit, presenting apricot and peach aroma. The OAVs of \(\gamma\)-hexalactone and \(\gamma\)-nonanolactone were below 1. Therefore, \(\gamma\)-butyrolactone and \(\gamma\)-decalactone were the main peach-aroma contributors in peach spirit. The differences in lactone concentrations and OAVs between the two peach spirits were in agreement with the typical peach aroma property being stronger in the pervaporation produced peach spirit. Due to high carbon content and the presence of oxygen-containing heterocycles, lactones has high hydrophobicity, which account for the abundance of lactones in pervaporation produced peach spirit [37; 39; 40]. On the other hand, all these lactones had high boiling points (\(>\)200 \({}^{\circ}\)C), which resulted in being concentrated hardly by distillation. It implies that producing peach spirit by pervaporation membrane technology was beneficial to retaining the typical aroma of peach. Terpenoids are important aroma compounds contributing to floral and sweet odor, with relatively low thresholds. Except dihydro-\(\beta\)-ionol, all the terpenids identified by GC-O were quantified in the two peach spirits. A total of 6 terpenids were quantified in distilled peach spirit. Among them, citronellol, (E)-\(\beta\)-damascenone, and linalool had OAVs greater than or equal to 1, presenting rose, sweet and floral notes, respectively. Based on the OAV and FD factors, (E)-\(\beta\)-damascenone was potentially the most critical aroma compound in the distilled peach spirit, and it was also suggested as an important aroma compound in Cognac by [PERSON] and [PERSON] [36]. A total of 3 terpenids were quantified in pervaporation produced peach spirit, (E)-\(\beta\)-damascenone and eugenol having OAVs greater than 1.