## 3 Results and Discussion
### Quantification and OAV Analysis of Aroma Compounds
A comparative analysis of the terpenids showed that citronellol and (E)\(\beta\)-damascenone were more concentrated in the distilled peach spirit, with OAVs 20 times higher than those in the pervaporation produced peach spirit. The above results indicated that the contribution of terpenoids is greater in distilled peach spirit than in pervaporation produced peach spirit. The glycoside-bound form terpenoid is usually 2-8 times that of free form [41]. Acid hydrolysis under mild conditions and continuous heating could liberate volatile compounds from their glycosyl portion during the Charente pot distillation process [42; 43]. For example, the heat treatment of diol precursors, as well as the thermal degradation of \(\beta\)-carotene in aqueous media, could form and additionally convert many norisoprenoids [43; 44]. Moreover, in the previous research, (E)-\(\beta\)-damascenone has also been proved to be formed during the distillation process, and the concentration of (E)-\(\beta\)-damascenone increased along with the distillation time [45]. Therefore, distillation process is benefit for terpenoids accumulation, while the terpenoid concentration in the pervaporation produced peach spirit was lower due to lack of heating treatment during pervaporation. However, eugenol showed a different accumulation pattern and was only detected in pervaporation produced peach spirit. This might be due to the fact that the chemical structure of eugenol contains a phenyl group, which is more hydrophobic than other terpenoids and facilitates concentrating by pervaporation [37; 40]. A total of 7 volatile acids were quantified in the peach spirits, which mainly contributed to the acidic aroma. The concentration of each acid in the pervaporation produced peach spirit was significantly higher than those in the distilled peach spirit, except decanoic acid, which was only detected in the distilled peach spirit. In the distilled peach spirit, the OAVs of all the acids were less than 1. In the pervaporation produced peach spirit, the concentrations of 2-methylpropanoic acid and 3-methylbutanoic acid were the highest among the acids, with OAV of 8 and 4, respectively. The presence of high concentrations of 3-methylbutanol has also been reported in the production of the Brazilian spirit Cachaca using pervaporation [17]. Other acids had extremely low contributions and even made no effect on the overall aroma based on the OAVs. The above results indicated that, compared to other compound classes, acids presented little sensory attribute in the peach spirits. While the comparison between the two peach wines, because the pervaporation process was more conducive to the enrichment of acids, the acidic aroma property was significantly stronger in the pervaporation produced peach spirit. [PERSON] et al. [46] explained that as acids had higher boiling points than ethanol, losses would occur during the distillation process, while the acids were not affected by the boiling points during the pervaporation. In the peach spirits, 1,1-diethoxyethane, the only detected acetal compound, had markedly high OAVs with concentrations of more than 4000 \(\mathrm{\SIUnitSymbolMicro g}\)/L, presenting a sweet sensory attribute. As for furans, furfural was quantified with OAVs of 2 and 3 in the distilled peach spirit and pervaporation produced peach spirit, respectively. Although ethyl 2-fruorate was also detected in the distilled peach spirit, the OAV was below 1. Six aromatic compounds with relatively high FD factors were quantified, but all of them had little aroma contribution according to the OAVs, except phenethyl acetate in the distilled peach spirit.