## 3 Results
### OAVs  
As the samples were significantly concentrated before GC-O analysis, the osme values could not indicate the final impact of these aroma-active compounds on the overall aroma in authentic liquors. So, OAVs were calculated to further confirm the contributions of these compounds [38]. The results are listed in Table 3. There were 28 aroma compounds with OAVs > 1 simultaneously in four samples, which indicated that these odorants might contribute to the characteristic aroma. The most important aroma compounds (OAVs > 100) in all samples were 3-methylbutanal, \(\beta\)-damascenone and ethyl octanoate. Dimethyl trisulfide, ethyl hexanoate, ethyl acetate, 3-methylbutyl acetate, 1,1-diethoxyethane, ethyl butanoate, hexanal, ethyl 2-methylpropanoate, ethyl 3-methylbutanoate, ethyl lactate and ethyl pentanoate could also be significant according to their high OAVs (>10). Interestingly, recent studies have found that ethyl hexanoate, with the aroma of pineapple, also makes great contributions to the pungency and sweetness perception of Baijiu [35; 39]. Compounds, including 1-octen-3-ol, ethyl 2-methylbutanoate, 2-methylpropanol, butanoic acid, acetic acid, pentanoic acid, 1-propanol, 1-butanol, guaicaol, phenylacetaldehyde, \(\beta\)-ionone, hexanoic acid, 3-methylbutanoic acid, 3-methylbutanol were other aroma contributors (OAVs > 1). The OAVs of nonanal and ethyl dodecanoate were greater than 1 only in F30. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Aroma Compound**} & \multirow{2}{*}{**Threshold (\(\text{ug/L}\))**} & \multicolumn{4}{c}{**OAVs**} \\ \cline{3-6}  & & & **F00** & **F10** & **F20** & **F30** \\ \hline
3 & 3-Methylbutanal & 17\({}^{\text{a}}\) & 595.53 & 671.19 & 606.69 & 640.78 \\
72 & \(\beta\)-Damascenone & 0.12\({}^{\text{a}}\) & 255.08 & 438.76 & 352.45 & 420.06 \\
38 & Ethyl octanoate & 12.9\({}^{\text{a}}\) & 191.53 & 263.78 & 282.73 & 323.31 \\
34 & Dimethyl trisulfide & 0.36\({}^{\text{a}}\) & 93.25 & 103.95 & 90.36 & 104.44 \\
22 & Ethyl hexanoate & 55.3\({}^{\text{a}}\) & 74.24 & 85.98 & 93.92 & 99.93 \\
4 & Ethyl acetate & 32,600\({}^{\text{a}}\) & 39.33 & 30.87 & 36.99 & 37.11 \\
17 & 3-Methylbut acetate & 93.9\({}^{\text{a}}\) & 32.38 & 35.13 & 42.69 & 43.69 \\
2 & 1-Diethoxyethane & 2090\({}^{\text{a}}\) & 24.44 & 31.31 & 28.84 & 30.67 \\
9 & Ethyl butanoate & 81.5\({}^{\text{a}}\) & 23.85 & 25.39 & 29.27 & 33.85 \\
14 & Hexanal & 25.5\({}^{\text{a}}\) & 20.46 & 16.72 & 29.67 & 23.92 \\
6 & Ethyl 2-methylpropanoate & 57.5\({}^{\text{a}}\) & 16.81 & 21.79 & 21.63 & 27.75 \\
13 & Ethyl 3-methylbutanoate & 6.89\({}^{\text{a}}\) & 15.62 & 18.53 & 20.03 & 33.46 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The odor activity values (OAVs) of aroma compounds in four different grades of FJ. To visually compare the differences in those aroma-active compounds with OAVs > 1, the histogram of their concentrations in the four different grades of FJ is shown in Figure S2. Esters made a great contribution to the pleasant fruity and floral aroma of LFB. In F30, there were 12 esters considered as the main contributors of aroma, including ethyl octanoate, ethyl hexanoate, ethyl acetate, 3-methylbutyl acetate, ethyl 2-methylpropanoate, ethyl 3-methylbutanoate, ethyl lactate, ethyl pentanoate, ethyl 2-methylbutanoate, ethyl decanoate, and ethyl dodecanoate. Aroma compounds, whose concentrations rose with the increase of the grade, may be the reason for the differences in aroma quality. Among these esters, the higher the sample grade, the higher the concentrations of ethyl butanoate,  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No.