## 3 Results and Discussion
### GC-FID and SBSE-GC-MS Analysis  
By GC-O analysis, a total of 57 compounds were identified to contribute to the aroma of Xiaoqu liquor, and their contributions were quantified by the FD values. However, the extraction and condensation process might have caused some loss of the aroma compounds, which might affect the evaluation results of the aroma [15]. Hence, it is necessary to conduct quantitative analysis of the 57 compounds and calculate their OAVs, so as to more accurately demonstrate the contribution of each compound to the overall aroma of Xiaoqu liquor. To this end, GC-FID combined with SBSE-GC-MS was used for the quantitative analysis, which has been validated to be an effective method in previous studies. The standard curve and the contents of compounds are shown in Table 3. In Xiaoqu liquor, the content of ethyl octanoate (5502.8 \(\mu\)g/L) was significantly higher than that in Daqu liquor (2163.91 \(\mu\)g/L), but the contents of ethyl lactate (442,370 \(\mu\)g/L) and ethyl acetate (537,920 \(\mu\)g/L) were lower [11]. Besides, higher contents of acetaldehyde (151,980 \(\mu\)g/L), isoamyl acetate (7099.8 \(\mu\)g/L), and ethyl laurate (2827.21 \(\mu\)g/L) were found in Xiaoqu liquor. It can be speculated that different contents of such important aroma compounds contribute to the unique flavor of Xiaoqu liquor. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Compounds**} & \multicolumn{2}{c}{**RI**} & \multirow{2}{*}{**FD**} & \multirow{2}{*}{**Identification**} & \multirow{2}{*}{**Aroma Description**} \\ \cline{3-4} \cline{6-6}  & & **DB-FEAP** & & & & \\ \hline
36 & \(N\)-nonanol & 1647 & 1168 & 2 & MS, Std, Odor, RI & Lipid, floral \\
37 & Isovaleric acid & 1659 & 842 & 4 & MS, Std, Odor, RI & Sweed odor \\
38 & Ethyl benzoate & 1660 & 1165 & 2 & MS, Std, Odor, RI & Flower \\
39 & Diethyl succinate & 1665 & 1188 & 2 & MS, Std, Odor, RI & Sweet \\
40 & 2-thiophene formaldehyde & 1710 & - & 2 & MS, Odor, RI & Cooked cabbage \\
41 & Ethyl undecanoate & 1716 & - & 2 & MS, Odor, RI & Floral \\
42 & Valeric acid & 1719 & 903 & 16 & MS, Std, Odor, RI & Cellar mud odor, sweat odor odor, acid odor \\
43 & Ethyl phenylacetate & 1788 & 1241 & 2 & MS, Std, Odor, RI & fruity \\
44 & Phenethyl acetate & 1815 & 1259 & 2 & MS, Std, Odor, RI & Rose, floral, rubber \\
45 & Ethyl laurate & 1824 & 1589 & 8 & MS, Std, Odor, RI & Sweet, fruity \\
46 & Hexanoic acid & 1845 & 980 & 2 & MS, Std, Odor, RI & Sweed odor, animal odor, acid odor \\
47 & Ethyl phenyl propionate & 1885 & 1348 & 1 & MS, Std, Odor, RI & Jack fruit, fruit drops, honey \\
48 & Phenethyl alcohol & 1907 & 1110 & 2 & MS, Std, Odor, RI & Rose, Chinese rose \\
49 & Hepatanoic acid & 1919 & - & 1 & MS, Std, Odor, RI & Acid odor, sweat odor \\
50 & 4-methylguaiacol & 1966 & 1087 & 1 & MS, Std, Odor, RI & Smoking, soy sauce \\
51 & Ethyl myristate & 2036 & 1688 & 4 & MS, Std, Odor, RI & Floral \\
52 & 4-ethylgaaiacol & 2053 & 1277 & 1 & MS, Std, Odor, RI & Melon, fruity, sweet \\
53 & Caprylic & 2059 & - & 2 & MS, Std, Odor, RI & Fatty \\
54 & \(\gamma\)-nonalcone & 2072 & 1368 & 4 & MS, Std, Odor, RI & Cream, coconut, cream Biscuit \\
55 & Ethyl palmitate & 2255 & - & 4 & MS, Std, Odor, RI & Nuts \\
56 & Ethyl oleate & 2477 & - & 1 & MS, Std, Odor, RI & Fatty \\
57 & Ethyl linoleate & 2528 & - & 1 & MS, Std, Odor, RI & Fatty \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._