## 3 Results and Discussion
### OAV Analysis  
According to [PERSON]'s theory, aroma components in food products with a high aroma concentration and a low threshold value are probably the characteristic aroma of that food product. In general, the contribution of volatile compounds to the aroma characteristics of the samples in combination with the OAVs needs to be further determined [11; 35; 36]. The key volatile compounds were identified in each sample based on the OAV >1 [37]. A total of 27 key aroma substances were determined for all green huajiao samples, and the threshold values and aroma descriptions of these aroma compounds are shown in Supplementary Table S3. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Attributes**} & \multicolumn{8}{c}{**Sum of Ranks**} \\ \cline{2-7}  & **G1** & **G2** & **G3** & **G4** & **G5** & **G6** & **G7** \\ \hline Pungent & 46 & 48 & 23 & 50 & 14 & 29 & 14 \\ Citrusy & 21 & 41 & 40 & 14 & 50 & 16 & 42 \\ Floral & 45 & 49 & 33 & 46 & 13 & 19 & 19 \\ Lemony & 20 & 17 & 45 & 22 & 48 & 25 & 47 \\ Green & 25 & 16 & 49 & 13 & 38 & 46 & 37 \\ Minty & 27 & 11 & 46 & 19 & 37 & 44 & 40 \\ Herbal & 40 & 43 & 14 & 52 & 21 & 38 & 16 \\ Sweet & 42 & 43 & 13 & 46 & 15 & 44 & 21 \\ \hline \end{tabular}
\end{table} 
Table 2: Rank and GPA analysis of different green huajiao samples. As shown in Table 3, the OAV values of key aroma compounds in the seven green huajiao samples differed significantly (\(p<0.05\)). The OAVs of three aroma compounds, myrcene(L4), limonene (L8) and linalool (L14), were the highest, exceeding 10,000. These three aroma compounds are reported as the main aromatic characteristics in the flavor of huajiao samples [4]. The OAV values of \(\alpha\)-pinene (L1), ashinene (L2), 1,8-cineole (L9), ocimene (L10), linalool oxide (L12), \(\alpha\)-terpinene (L13), thujone (L15), citronellal (L16), carvone (L21) and linalyl acetate (L22) were also higher in most huajiao samples, with OAVs between 1000 and 10,000. These results indicated that they are also the main aroma compounds contributing to the characterization of the aroma of most of the huajiao samples. The OAV of trans-nerolidol compound in sample G6 (Jiangjin, Chongqing) was significantly higher than that in the other Sichuan huajiao samples, which might be due to the different geographical locations. Figure 5: Overall characteristics of volatile compounds of seven green huajiao samples (**A**): Venn diagram; (**B**): contents of volatile compounds; (**C**): heatmap of the content of 69 volatile compounds). (Note: a–f indicates the significant difference in OAI values between the huajiao samples). The clustering heatmap (OAV) of 27 key aroma compounds (OAV > 1) of seven green huajiao samples is shown in Figure 6, which illustrates aroma characteristic differences of varied huajiao samples. The color coding is graded according to the scale from blue (low OAV) to red (high OAV) [38]. The seven samples were categorized into three clusters. Cluster 1 included G1, G2 and G4. These three samples had higher OAVs of terpenes, including \(\alpha\)-pinene (L1), sabinene (L2), myrcene (L4), limonene (L8), ocimee (L10) linalyl acetate (L22) and alcohols of 1,8-cineeole (L9) and terpinen-4-ol (L17). These aroma compounds were the key aroma compounds that distinguished samples G1, G2 and G4 from the other samples [36]. Cluster 2 included G3, G5 and G7. These samples had higher OAV of linalool (L14), which is mainly sweet and floral. In addition, the compounds linalool oxide(L12), \(\alpha\)-terpinene (L13), citronellal (L16) and carvone (L21) in samples G5 and G7 also had higher OAVs, while the compounds 1,8-cineeole (L9) and \(\alpha\)-terpinen (L18) in G3 had higher OAVs. G6 clustered by itself, with higher OAVs of phellandrene (L5), meridold (L26), trans-caryophyllene (L25) \(\alpha\)-terpineol (L18) and carvool (L19). Green huajiao from different sources exhibited differential main aroma compounds, which is more consistent with existing reports.