## 2 Results and Discussion
### Identification of Aroma Compounds in Young and Aged Nongxiangxing Baijiu by GC-O/MS
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**No**} & \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**RI \({}^{\text{a}}\)**} & \multirow{2}{*}{**RIL \({}^{\text{b}}\)**} & \multicolumn{2}{c}{**Odor**} & \multicolumn{2}{c}{**FD \({}^{\text{c}}\)**} & \multirow{2}{*}{**Identification \({}^{\text{d}}\)**} \\ \cline{5-8}  & & & & & **Texars** & & **Texars** & & **Texars** \\ \hline \multicolumn{8}{c}{Esters} \\
1 & Ethyl ethanoate & 893 & 902 & Fruity & 1024 & 1024 & 2048 & RI, MS, Std, Aroma \\
2 & Methyl hexanoate & 1108 & 1183 & Fruity & 32 & 4 & 4 & RI, MS, Aroma \\
3 & Ethyl hexanoate & 1183 & 1235 & Fruity & 2048 & 1024 & 1024 & RI, MS, Std, Aroma \\
4 & Pentyl lutanoate & 1199 & 1326 & Banana & 8 & 4 & 4 & RI, MS, Aroma \\
5 & Propyl hexanoate & 1253 & 1293 & Pineapple & 64 & 16 & RI, MS, Std, Aroma \\
6 & Ethyl heptanoate & 1271 & 1342 & Pineapple & 32 & 16 & 16 & RI, MS, Std, Aroma \\
7 & 2-Methylpropyl hexanoate & 1286 & 1362 & Fruity & 8 & 4 & 4 & RI, MS, Std, Aroma \\
8 & Butyl hexanoate & 1352 & 1384 & Fruity & 8 & 4 & 4 & RI, MS, Std, Aroma \\
9 & Hexyl butanoate & 1355 & 1388 & Soapy, fruity & 4 & 4 & 4 & RI, MS, Aroma \\
10 & Ethyl octanoate & 1379 & 1434 & Fruity, waxy & 4 & 4 & 4 & RI, MS, Std, Aroma \\
11 & 3-Methylbutyl butanoate & 1402 & 1459 & Banana & 64 & 32 & 64 & RI, MS, Std, Aroma \\
12 & Ethyl nonanoate & 1486 & 1533 & Fruity & 8 & 8 & 16 & RI, MS, Std, Aroma \\
13 & Hexyl hexanoate & 1571 & 1609 & Herbal, grass & 4 & 4 & 8 & RI, MS, Std, Aroma \\
14 & Ethyl decanoate & 1606 & 1634 & Waxy, fruity & 4 & 2 & 16 & RI, MS, Std, Aroma \\
15 & Diethyl butanedioate & 1659 & 1677 & Fruity & 16 & 4 & 4 & RI, MS, Std, Aroma \\
16 & Ethyl dodecanoate & 1803 & 1860 & Waxy, soapy & 4 & 8 & 8 & RI, MS, Std, Aroma \\
17 & Ethyl butanoate & 1023 & 1025 & Fruity & 1024 & 1024 & 512 & RI, MS, Std, Aroma \\
18 & 3-Methylbutyl ethanoate & 1128 & 1131 & Sweet, fruity & 4 & 16 & 16 & RI, MS, Std, Aroma \\
19 & Ethyl pentanoate & 1122 & 1159 & Fruity & 32 & 16 & 8 & RI, MS, Std, Aroma \\
20 & Ethyl hexadecanoate & 2255 & 2265 & Waxy, fruity & 2 & 4 & 4 & RI, MS, Std, Aroma \\
21 & Ethyl (\(\lx@notemark{2}\))-octadec-9-anoate & 2479 & 2476 & Fatty, oily & 2 & 2 & 2 & RI, MS, Std, Aroma \\
22 & Ethyl (\(\lx@notemark{2}\),122)-octadec-9,12-dienoate & 2521 & 2521 & Fatty, oily & 4 & 2 & 2 & RI, MS, Std, Aroma \\
23 & Ethyl 2-methyl butanoate & 1040 & 1053 & Fruity & 256 & 64 & 32 & RI, MS, Std, Aroma \\
24 & Ethyl 3-methylbutanoate & 1055 & 1060 & Sweet, apple & 128 & 64 & 64 & RI, MS, Aroma \\
25 & Ethyl 4-methylprotonate & 1189 & 1197 & Pruity & 64 & 32 & 16 & RI, MS, Std, Aroma \\
26 & Ethyl 2-hydroxy-4-methylpentanoate & 1508 & 1516 & Blackberry & 4 & 8 & 16 & RI, MS, Aroma \\
27 & Ethyl cyclohexamcarboxylate & 1414 & 1424 & Fruity & 32 & 64 & 32 & RI, MS, Std, Aroma \\ \hline \multicolumn{8}{c}{Alcohols} \\
28 & Butan-2-ol & 938 & 1020 & Sweet & 512 & 256 & 256 & RI, MS, Aroma \\
29 & Propan-1-ol & 972 & 1035 & Alcoholic & 64 & 32 & 16 & RI, MS, Std, Aroma \\
30 & 2-Methylpropan-1-ol & 1049 & 1078 & Winery & 4 & 4 & 4 & RI, MS, Aroma \\
31 & Pentan-2-ol & 1078 & 1114 & Orily, & 256 & 128 & 256 & RI, MS, Std, Aroma \\
32 & Butan-1-ol & 1092 & 1137 & Fusel, sweet & 128 & 64 & 16 & RI, MS, Aroma \\
33 & 3-Methylbutan-1-ol & 1135 & 1201 & Femmented & 128 & 64 & 64 & RI, MS, Aroma \\
34 & Hexan-2-ol & 1190 & 1210 & Winery & 16 & 8 & 8 & RI, MS, Aroma \\
35 & 3-Methylbutan-2-ol & 1220 & 1256 & Fermented, & 4 & 4 & 4 & RI, MS, Aroma \\
36 & 3-Methylbutan-3-en-1-ol & 1225 & 1246 & Sweet, fruity & 4 & 4 & 4 & RI, MS, Aroma \\
37 & Heptan-2-ol & 1274 & 1306 & Citrus, & & 4 & 8 & 4 & RI, MS, Std, Aroma \\
38 & Hexan-1-ol & 1313 & 1341 & Herbal & 64 & 32 & 4 & RI, MS, Aroma \\
39 & Octan-3-ol & 1430 & 1462 & Mushroom & 32 & 32 & 64 & RI, MS, Std, Aroma \\
40 & Heptan-1-ol & 1410 & 1442 & Green, & 16 & 16 & 32 & RI, MS, Std, Aroma \\
41 & Octan-1-ol & 1514 & 1554 & Waxy & 16 & 4 & 4 & RI, MS, Std, Aroma \\
42 & 2-Methylbutan-1-ol & 1204 & 1197 & Fusel, & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & & \\  & & & &  
\begin{table}
\begin{tabular}{l c c c c c c c c c} \hline \hline \multirow{2}{*}{**No**} & \multirow{2}{*}{**Compound**} & \multirow{2}{*}{**RI \({}^{\bullet}\)**} & \multirow{2}{*}{**RIL \({}^{\text{b}}\)**} & \multicolumn{3}{c}{**Odor**} & \multicolumn{3}{c}{**FD \({}^{\text{c}}\)**} & \multirow{2}{*}{**Identification \({}^{\text{d}}\)**} \\ \cline{5-8}  & & & & & **Descriptor** & **15** & **years** & **5 years** & **0 years** & \\ \hline
51 & Heptanoic acid & 1928 & 1960 & Sour, cheesy & 8 & 4 & 2 & RI, MS, Std, Aroma \\
52 & Octanoic acid & 2035 & 2070 & Sweaty, cheesy & 4 & 4 & 2 & RI, MS, Std, Aroma \\
53 & Propanoic acid & 1530 & 1535 & Cheesy & 16 & 8 & 2 & RI, MS, Std, Aroma \\
54 & Nonanoic acid & 2162 & 2169 & Waxy, cheesy & 16 & 16 & 64 & RI, MS, Std, Aroma \\ \hline \multicolumn{8}{c}{Aldehydes and ketones} & \multirow{8}{*}{Oct-1-en-3-one} & \multirow{8}{*}{1309} & \multirow{8}{*}{1306} & Mushroom, \multirow{8}{*}{16} & \multirow{8}{*}{32} & \multirow{8}{*}{64} & \multirow{8}{*}{RI, MS, Std, Aroma} \\
55 & Oct-1-en-3-one & & & & & & & \\  & & & & & & & & \\
56 & Oct-3-en-2-one & 1388 & 1408 & \multirow{8}{*}{892} & \multirow{8}{*}{65} & \multirow{8}{*}{16} & \multirow{8}{*}{RI, MS, Aroma} \\
57 & 1,1-Diethoxyethane & 892 & 892 & Green, nutty & 512 & 64 & 64 & RI, MS, Std, Aroma \\
58 & 3-Methylbutanal & 928 & 952 & Aldehyde, \multirow{8}{*}{32} & \multirow{8}{*}{16} & \multirow{8}{*}{4} & \multirow{8}{*}{RI, MS, Std, Aroma} \\
59 & Pentan-2-one & 1009 & 1003 & Fruify & 16 & 16 & 4 & RI, MS, Std, Aroma \\
60 & 3-Hydroxybutan-2-one & 1280 & 1305 & \multirow{8}{*}{1305} & Battery, \multirow{8}{*}{130} & \multirow{8}{*}{16} & \multirow{8}{*}{4} & \multirow{8}{*}{RI, MS, Std, Aroma} \\
61 & Butane-2,3-dione & 1005 & 977 & & & & & & \\  & & & & & & & & \\  & & & & & & & & & \\
62 & (E)-Oct-2-enal & 1430 & 1433 & Green, \multirow{8}{*}{128} & \multirow{8}{*}{32} & \multirow{8}{*}{16} & \multirow{8}{*}{RI, MS, Std, Aroma} \\
63 & (E)-Non-2-enal & 1542 & 1551 & & & & & & \\  & & & & & & & & \\
64 & (E,Z)-Nona-2,6-dienal & 1572 & 1591 & \multirow{8}{*}{16} & \multirow{8}{*}{4} & \multirow{8}{*}{RI, MS, Std, Aroma} \\
65 & (E,E)-Nona-2,4-dienal & 1696 & 1686 & Fatty, green & 16 & 16 & 4 & RI, MS, Std, Aroma \\
66 & (E,E)-Deca-2,4-dienal & 1819 & 1802 & Citrus, green & 64 & 64 & 4 & RI, MS, Aroma \\
67 & (E)-Hept-2-enal & 1309 & 1314 & Green, fatty & 4 & 4 & 2 & RI, MS, Std, Aroma \\ \hline \multicolumn{8}{c}{Terpenoids} & \multirow{8}{*}{8-damasceneo} & \multirow{8}{*}{1818} & 1827 & Floral & 512 & 64 & 32 & RI, MS, Std, Aroma \\
69 & \(\beta\)-Ionone & 1947 & 1958 & Floral & 64 & 32 & 32 & RI, MS, Aroma \\
70 & Linalool & 1552 & 1579 & Floral, citrus & 32 & 4 & 2 & RI, MS, Aroma \\
71 & Nerol & 1806 & 1821 & Floral & 16 & 4 & 4 & RI, MS, Aroma \\ \hline \multicolumn{8}{c}{Lactones} & \multirow{8}{*}{72} & Butan-4-olide & 1611 & 1626 & Creamy, oily & 64 & 32 & 32 & RI, MS, Std, Aroma \\
73 & Hexa-4-olide & 1695 & 1703 & Herbal & 4 & 2 & 2 & RI, MS, Std, Aroma \\
74 & Nonan-4-olide & 2031 & 2024 & Coconut & 128 & 64 & 128 & RI, MS, Std, Aroma \\ \hline \multicolumn{8}{c}{Aromatics} & \multirow{8}{*}{75} & \multirow{8}{*}{\(\beta\)-phenylethanol} & \multirow{8}{*}{1923} & 1906 & Floral & 256 & 128 & 16 & RI, MS, Std, Aroma \\
76 & 2-Phenylethanolanal & 1634 & 1642 & Green, sweet & 128 & 16 & 8 & RI, MS, Std, Aroma \\
77 & Benzaldehyde & 1508 & 1534 & Fruify & 8 & 4 & 2 & RI, MS, Std, Aroma \\
78 & Ethyl 3-phenylpropionate & 1870 & 1880 & Floral, honey & 2048 & 256 & 256 & 256 & RI, MS, Std, Aroma \\
79 & Ethyl 2-phenylethanoate & 1764 & 1797 & Floral & 128 & 128 & 16 & RI, MS, Std, Aroma \\ \hline \multicolumn{8}{c}{Furans} & \multirow{8}{*}{2-(Diethoxymethyl)furan} & \multirow{8}{*}{1442} & 1432 & Mushroom & 16 & 16 & 64 & RI, Aroma \\
81 & Furan-2-carbaldehyde & 1458 & 1466 & Baked bread & 16 & 32 & 64 & RI, MS, Std, Aroma \\
82 & 1-(Furan-2-yl)pentan-1-one & 1737 & 1747 & Sweet, \multirow{8}{*}{2} & \multirow{8}{*}{4} & \multirow{8}{*}{RI, ARoma, Aroma} \\
83 & (Furan-2-yl)methanol & 1666 & 1647 & Bready & 4 & 4 & 8 & RI, MS, Std, Aroma \\ \hline \multicolumn{8}{c}{Sulfur-containing compounds} & \multirow{8}{*}{2-(Methylsulfanyl)}\(\_\)ethan-1-olol} & \multirow{8}{*}{1515} & \multirow{8}{*}{1486} & Sulfurous, \multirow{8}{*}{1486} & Sulfurous, \multirow{8}{*}{256} & \multirow{8}{*}{32} & \multirow{8}{*}{32} & \multirow{8}{*}{RI, MS, Aroma} \\
84 & 2-(Methylsulfanyl)}\(\_\)ethan-1-ol & & & & & & \\  & & & & & & & \\  & & & & & & & & \\  & & & & & & & & \\  & & & & & & & & & \\
85 & 3-(Methylsulfanyl)propan-1-ol & & 1719 & 1719 & Meaty, onion & 8 & 16 & 8 & RI, MS, Std, Aroma \\ \hline \multicolumn{8}{c}{Pyrazines} & \multirow{8}{*}{87} & \multirow{8}{*}{2,3,5-Trimethylpyrazine} & \multirow{8}{*}{1392} & \multirow{8}{*}{1392} & \multirow{8}{*}{Nutty, earthy} & \multirow{8}{*}{32} & \multirow{8}{*}{4} & \multirow{8}{*}{4} & \multirow{8}{*}{RI, MS, Std, Aroma} \\
88 & 2,3,5,6-Tetramethylpyrazine & 1472 & 1477 & Nutty & 64 & 8 & 16 & RI, MS, Std, Aroma \\ \hline \multicolumn{8}{c}{Phenolic compounds} & \multirow{8}{*}{4-Methyl-2-methoxyphenol} & \multirow{8}{*}{1945} & \multirow{8}{*}{1953} & Woody & 64 & 16 & 16 & RI, MS, Std, Aroma \\
90 & Phenol & 1987 & 2030 & \multirow{8}{*}{Pastic, rubber} & \multirow{8}{*}{4} & \multirow{8