## 3 Results and Discussion
### Effect of BTH Treatment on the Activities of Key Enzymes of LOX Pathway
However, HPL activity was  
Figure 4: Hierarchical heatmap of C6 compounds in control (CK) and BTH-treated (BTH) Cabernet Gernischt grapes during grape ripening. The color scale shows that compounds with high concentrations range from white to dark red, while compounds with low concentrations range from white to dark blue. “(F)” and “(B)” indicate free and bound aromas, respectively. Each line consists of three measurements of the same sample to achieve minimum error. The first digit of the sample name indicates the number of weeks post-flowering. In the second position, “B” indicates BTH-treated grapes and “C” indicates CK grapes. For example, “3C1” represents the first parallel measurement of CK grapes at 3 weeks post-flowering. significantly lower in BTH-treated grapes than in the CK at end-veraison stage, and this difference in enzyme activities resulted in variations in the concentration of C6 aldehydes and C6 alcohols. A significant decrease in C6 compounds was also obtained by silencing HPL in potatoes [56] The findings suggests that BTH inhibits the conversion of precursor 13-hydroperoxy-octadecatrienoic and 13-hydroperoxy-octadecadienoic acids to C6 aldehydes and C6 aldehydes to C6 alcohols by decreasing the activities of HPL and ADH and promotes the conversion of C6 alcohols to C6 esters by increasing AAT activity. The concentration of bound C6 compounds in Cabernet Gernischt grapes was much lower than that of the free form, indicating that the majority of C6 compounds in these grapes exist in their free form. The developmental patterns of C6 aldehydes and alcohols, both in bound and free forms, exhibit similar trends. However, C6 esters demonstrate contrasting patterns. Interestingly, the significant effects of BTH treatments on bound C6 aldehydes and C6 alcohols were mainly observed before mid-veraison (weeks 7-11), whereas the significant effects on bound C6 esters were mainly observed after veraison (weeks 13-15). This suggests a lag in the impact of BTH treatment on C6 compounds, as elaborated in the OPLS-DA analysis score plot (Figure 5A). BTH probably increased the accumulation of linoleic and linoleic acid and metabolic substrates during the end-swelling and mid-veraison stages (weeks 7 and 9, respectively). This, in turn, significantly affected the activities of LOX, HPL, and ADH enzymes during end-veraison (week 11), consequently impacting the concentration of C6 compounds in mid-ripening and ripe grapes. Previous studies have shown that BTH significantly affects the concentration of C6 compounds and that the increase in C6 aldehydes may be due to the alteration of fatty acid formation pathways by BTH [22; 31]. However, in our study, linolenic and linoleic acids were significantly reduced, and BTH appeared to continuously promote the whole metabolic process as the grapes progressed through the grape ripening process. The increase in C6 ester concentration in BTH-treated grapes is strong evidence for this promotion [22]. Figure 5: OPLS-DA analysis scores plot (**A**) and VIP scores plot (**B**) of C6 compounds in control (CK) and BTH-treated (BTH) Cabernet Gernischt grapes during grape ripening. “(F)” and “(B)” indicate free and bound aromas, respectively. Sample points with suffixes 1, 2, and 3 are three measurements of the same sample in order to attain minimum error. The first digit of the sample name indicates the number of weeks after flowering. In the second position, “B” indicates BTH-treated grapes and “C” indicates CK grapes. For example, “3C1” represents the first parallel measurement of CK grapes at 3 weeks post-flowering.