# HS-SPME Combined with GC-MS/O to Analyze the Flavor of Strong Aroma Baijiu _Daqu_
## 3 Results
### Analysis of Daqu at Different Maturity Stages by HS-SPME Combined with GC-MS
**} & \multirow{2}{*}{**Compound**} & \multicolumn{2}{c}{**CAS**} & \multirow{2}{*}{**RI**} & \multirow{2}{*}{**Identification \({}^{\text{a}}\)**} & \multicolumn{6}{c}{**Area Percentage \% \({}^{\text{b}}\)**} \\ \cline{5-10}  & & & & & & **S-0D** & **S-4D** & **S-6D** & **S-10D** & **S-22D** & **S-3M** \\ \hline Phenols & Phenol & 108-95-2 & 1993 & S,MS,RI & 0.400 & 0.041 & 0.054 & 0.874 & 0.285 & 0.373 \\
73 & 4-Ethly-2- & 2785-89.9 & 2015 & S,MS,RI & 3.002 & 13.076 & 17.783 & 0.555 & 0.943 & 0.490 \\
74 & 4-Ethlyphenol & 123-07-9 & 2142 & S,MS,RI & 0.141 & 0.091 & 0.112 & 0.071 & 0.034 & 0.137 \\
76 & 2-ethowy-4- & 7786-61-0 & 2177 & S,MS,RI & 0.646 & 3.237 & 8.710 & 0.969 & 0.696 & 0.319 \\  & 2,4-Bis(1,- & & & & & & & & \\
77 & dimethylethyl)- & 96-76-4 & 2296 & S,MS,RI & 10.538 & 0.135 & 0.291 & 1.228 & 0.611 & 0.962 \\  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ Ketones & & & & & & & & & & \\
78 & 3-Octanone & 106-68-3 & 1254 & S,MS,RI & — & 0.114 & 0.194 & — & — & — \\
79 & 2-Octanone & 111-13-7 & 1286 & S,MS,RI & 5.823 & 4.586 & 4.793 & 7.414 & 8.267 & 2.411 \\
80 & 6-Methyl-5-hepten-2- & 110-93-0 & 1340 & S,MS,RI & 0.296 & — & — & — & 0.316 \\
81 & 2-Nonanone & 821-55-6 & 1390 & S,MS,RI & — & — & 0.143 & — & 0.214 \\
82 & 3,5-Octadiene-2-one & 38284-27-4 & 1525 & MS,RI & 0.083 & — & — & — & — & 0.030 \\
83 & Acetophenone & 98-86-2 & 1661 & S,MS,RI & 0.701 & 0.082 & 0.104 & 0.594 & 0.521 & 0.871 \\
84 & Butyrophenone & 495-40-9 & 1805 & S,MS,RI & — & — & — & — & 0.158 \\ Subtotal & & & & & 6.903 & 4.782 & 5.090 & 8.151 & 8.788 & 4.000 \\ Nitrogenous & & & & & & & & & & \\ compounds & & & & & & & & & & \\
85 & 2-Methylpyrazine & 109-08-0 & 1268 & S,MS,RI & 0.170 & — & — & 0.274 & 0.298 & 0.321 \\
86 & 2,5-Dimethylpyrazine & 123-32-0 & 1324 & S,MS,RI & — & — & — & 0.054 & 0.157 & 0.186 \\
87 & 2,6-Dimethylpyrazine & 108-50-9 & 1330 & S,MS,RI & 0.216 & — & — & 0.374 & 0.330 & 0.626 \\
88 & 2,3-Dimethylpyrazine & 5910-89-4 & 1349 & S,MS,RI & — & — & — & 0.262 & 0.128 & 0.186 \\
89 & 2-Ethly-6- & 13925-03-6 & 1386 & S,MS,RI & — & — & — & 0.399 & 0.244 & 0.411 \\
90 & 2,3,5- & 14667-55-1 & 1405 & S,MS,RI & 0.097 & 0.029 & 0.070 & 1.440 & 0.905 & 1.542 \\  & Trimethylpyrazine & 2-Ethly-3,5- & 13925-07-0 & 1463 & S,MS,RI & — & — & — & 0.663 & 0.203 & 0.617 \\
91 & 2-Ethlyly-3,5- & & & & & & & & & \\
92 & Tetramethylpyrazine & 1124-11-4 & 1476 & S,MS,RI & 0.262 & — & — & 1.710 & 0.544 & 2.068 \\
93 & 2-Ethly-6- & & 13925-09-2 & 1494 & MS,RI & — & — & — & 0.403 & 0.490 & 0.533 \\  & methylpyrazine & 2-Ethly-3,5,6- & & 17398-16-2 & 1514 & MS,RI & — & — & 0.122 & 0.073 & 0.116 \\
94 & trimethylpyrazine & 1739-16-2 & 1514 & MS,RI & 0.138 & — & — & 0.030 & 0.086 & 0.139 \\
95 & 2-Acetypyrrole & 1072-83-9 & 1966 & S,MS,RI & 0.138 & — & — & 0.030 & 0.086 & 0.139 \\
96 & 1H-Pyrrole-2- & 1003-29-8 & 2013 & S,MS,RI & — & — & — & — & 0.482 \\  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\  & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ Aldehydes & & & & & & & & & & \\
97 & Hexanal & 66-25-1 & 1084 & MS,RI & 1.310 & — & — & 0.744 & 0.631 & 0.819 \\
98 & (_E_)-2-Heptension & 18829-55-5 & 1325 & MS,RI & 0.824 & — & — & — & — \\
99 & Nonanal & 124-19-6 & 1396 & S,MS,RI & 0.628 & 0.034 & 0.264 & 0.206 & 1.042 \\
100 & (_E_)-2-Octonal & 2548-87-0 & 1431 & S,MS,RI & 0.282 & — & — & — & 0.055 \\
101 & 3-Furaldehyde & 498-60-2 & 1474 & S,MS,RI & — & — & — & 0.095 & 0.118 \\
102 & Decanal & 112-31-2 & 15