## 3 Results and Discussion
### Effect of BTH Treatment on the Activities of Key Enzymes of LOX Pathway
This would accelerate the conversion of C6 aldehydes to C6 alcohols in veraison grapes, leading to a decrease in C6 aldehydes in ripe grapes treated with BTH. Notably, ADH activity decreased slightly in BTH-treated grapes at weeks 13 and 15, unlike the significant increase at weeks 9 and 11 (Figure 3C). It has been demonstrated that the decrease in ADH activity can explain the decrease in hexanol, E-2-hexenal, and E-3-hexenal during tomato refrigerated storage. _ADH1_ was found in seeds and young seedlings, and _ADH2_ accumulates in tomato fruit during ripening [59]. It can be hypothesized that the erratic trend of the ADH activity in our study is due to the tissue specificity of grapevine ADH and the interaction of E-2-hexenal. AAT transfers acyl groups from acyl-CoA to alcohol substrates to form esters, and C6 alcohols are further converted by AAT to hexyl acetate, Z-3-hexenyl acetate, and E-2-hexenyl acetate. AAT activity fluctuated during grape ripening, peaking at mid-ripening and then decreasing to levels comparable to that of mid-veraison (week 9). BTH treatment did not change the trend of AAT activity during grape ripening but significantly increased AAT activity at mid-ripening by 30.99% compared to the CK (Figure 3D). [PERSON] et al. [60] described in their study that the regulation of _MdAAT_ by SA is mediated by the induction of endogenous ethylene synthesis and the activation of the ethylene signaling pathway. They also observed that SA significantly suppressed the expression level of ethylene-producing genes (_ACO1_ and _ACS2_) [61]; inhibited the conversion of 1-aminocyclopropane-1-carboxylic acid to ethylene; and decreased the respiration rate depending on the inhibition of ethylene synthesis and stomata closure [61]. Therefore, BTH may inhibit ethylene synthesis by affecting the rate of grape cell respiration and the activities of two ethylene synthases. Consequently, this attenuates the regulation of AAT activity by ethylene and enhances AAT activity, since the regulation of AAT by BTH is dependent on influencing the respiration rate and ethylene synthesis, which are influenced by a variety of factors (varietyand developmental stage, etc.) during plant growth [60]. This may lead to a weakening of the effect of BTH on AAT, and AAT thus exhibits an unstable tendency. Effect of BTH Treatment on the Concentration of C6 Aldehydes, Alcohols, and Esters in Cabernet Germischt Grapes  
C6 aldehydes, alcohols, and esters can be synthesized from linoleic and linoleic acids through the catalytic action of LOX, HPL, ADH, and AAT enzymes. C6 aldehydes, alcohols, and esters in grapes exhibit herbal, citrus, and green leafy aromas. Hexanal, hexanol, E-2-hexanol, and E-2-hexanol are the direct precursors of hexyl acetate, an important compound that contributes to the aroma of grapes and wine during fermentation. During the ripening of grapes, a total of sixteen C6 compounds were detected, which included bound and free aldehydes (three), alcohols (three), and esters (two) (Figure 4). The same classes of free and bound C6 compounds were detected in both BTH-treated and CK grapes, indicating that the classes of C6 compounds remained unchanged following BTH treatment. The levels of free C6 aldehydes and C6 alcohols showed an increasing then decreasing trend during grape ripening. C6 alcohols increased sharply at veraison, while both C6 aldehydes and alcohols decreased at ripe grapes, with the trends corresponding to HPL and ADH activities, respectively. C6 esters showed a continuous decline during grape ripening, with the greatest decline in the Z-3-hexenyl acetate concentration (Figure 4). Furthermore, the concentration of C6 aldehydes and alcohols in ripe grapes treated with BTH was significantly lower compared to untreated grapes (CK), while the concentration of C6 esters was significantly higher in the BTH-treated grapes compared to the CK. The Importance of wine aroma on the sensory profile should not be overlooked, as it is a key factor that leads to the consumer's choice of wine [62].