## 3 Results and Discussion
### Pearson Correlation Analysis of linoleic Acid, Linolenic Acid, Enzyme Activity, and C6 Compounds  
To investigate the effects of BTH treatment on the correlation between substrates, activities of key enzymes, and free and bound C6 compounds, Pearson correlation analysis was carried out on the relevant indexes during grape ripening. The correlation analysis conducted on CK grapes revealed that the nodes corresponding to linolenic acid, ADH, and LOX exhibited a higher intensity of red coloration (Figure 6A), indicating a stronger correlation between these nodes and the other fractions under investigation. Specifically, linolenic acid, free C6 aldehydes, C6 alcohols, total free C6 compounds, LOX, ADH, and AAT showed highly significant positive correlations. This suggests that linolenic acid derived from grapes has a positive effect on the accumulation of C6 alcohols and the activity of enzymes involved in their production (see Table S4). Furthermore, the results revealed a strong positive correlation between ADH and C6 alcohols, as well as a strong negative correlation between ADH and free C6 esters. These findings suggest that ADH plays a role in the regulation of C6 alcohols and free C6 esters, promoting the former and inhibiting the latter. LOX also showed significant positive correlations with linolenic acid, free C6 aldehydes, C6 alcohols, and total free C6 compounds (Table S4), indicating that LOX and ADH are key pacemaker regulatory enzymes in the anabolic pathway of C6 compounds, which is consistent with the results reported by [PERSON] et al. [1]. Correlation analysis of BTH-treated grapes revealed that linolenic acid, LOX, HPL, and ADH exhibited the most significant correlations with the other fractions, as depicted in Figure 6B. BTH treatment resulted in an increased correlation between HPL and the other fractions, particularly a positive correlation with free and bound C6 aldehydes, as well as bound C6 compounds. This suggests that the BTH treatment has a positive regulatory effect on these fractions through HPL. Moreover, the inhibition of HPL in tobacco and _Arabidopsis_ also yielded significant reductions in C6 compounds, with a strong positive correlation between the expression of the gene encoding the HPL enzyme and total C6 compounds [64]. In contrast, free C6 esters were negatively correlated with linolenic acid, LOX, HPL, and ADH, suggesting that free C6 esters in grapes are indirectly influenced by these parameters, in addition to being directly influenced by AAT in a positive manner. BTH treatment enhanced the positive correlation between LOX and bound C6 aldehydes, C6 esters, and bound C6 compounds. Additionally, it was observed that BTH treatment decreased the correlation between LOX and linolenic acid. These findings suggest that BTH treatment has the potential to enhance the relationship between bound C6 compounds and other fractions by regulating LOX activity. Furthermore, BTH treatment can significantly increase the concentration of bound C6 compounds and facilitate the degradation of linolenic acid by LOX. The concentration of compounds in the aroma substances metabolism depends on the activity of key enzymes, substrate specificity, and substrate availability. The limiting factors of metabolism can be clarified by studying the correlation between the substrate concentration, enzyme activity, and product concentration. The observed variations in linoleic and linolenic acids in our investigation did not align with the trends observed for E-2-hexanal and hexanal. This indicates that the levels of linoleic and linolenic acids are unlikely to be the determining factor in the LOX pathway. Instead, it is more likely that the activity of LOX and ADH enzymes plays a significant role. The trends observed in AAT activity and hexyl acetate concentration were similar, suggesting that AAT is a limiting factor in determining the formation of C6 esters in grapes, which is similar to the results reported by [PERSON] et al. [65] but different from the findings of [PERSON] et al. [1].