## 2 Results
### Aroma Characteristics of 'Merlot' and 'Marselan' Wines Based on Odor Activity Value  
To investigate the potential impact of leaching and evolution of aroma compounds on odor characteristics during the viniification process of 'Marselan' and 'Merlot' dry red wines, we calculated the odor activity value (OAV) of the detected free-form aroma compounds in the wines. It should be noted that the OAV is calculated exclusively for the compounds with absolute quantification. The results are presented in Table S3. In general, aroma compounds with an OAV > 1 are considered to directly contribute to the sensory odor of the wine. The aroma compounds with OVA > 0.1 in wine samples at the end of malolactic fermentation (MLF end) and after 12 months of bottle storage (m12) were selected for OPLS-DA analysis due to the consideration of their interactions (Figure 3A,B). The analysis revealed 28 aroma compounds with OAV > 0.1. These compounds included eight alcohols (including three C6/C9 compounds, and five higher alcohols), 14 esters (including two acetates, 10 ethyl esters, and two other esters), one aldehyde, two volatile fatty acids, two terpen, and (\(E\))-\(\beta\)-damascenone (Figure 3C). The OPLS-DA model (R2X = 0.731, R2Y = 0.178) demonstrated high confidence (Figure 3A). The samples of 'MLF end' and'm12' were distinctly separated by the positive and negative halves of the x-axis, while the samples of 'Merlot' and 'Marselan' were well separated by the positive and negative halves of the y-axis. Figure 3B shows the loading plot, highlighting the aroma compounds with variance importance (VIP) > 1. Specifically, 1-octanol, citronell, (Z)-3-hexen-1-ol, methionol and (\(E\))-\(\beta\)-damascenone were distributed on the positive x-axis, indicating their higher abundance in wines at the end of maloalactic fermentation compared to those after one-year bottle storage. The OAV values of (\(E\))-\(\beta\)-damascenone reached 124.6 and 130.4 in the 'Merlot' and 'Marselan' wines, respectively, at the end of maloalactic fermentation (Table S3). These values were approximately twice as high as those found in bottles stored for 12 months. Conversely, isopentyl octanoate, and most ethyl esters were more abundant in the wines after one year of bottle storage, as evidenced by their location on the negative x-axis. These esters have fruity odors, such as apple, banana and lemon. However, their sensory contribution to the aroma of wine is generally lower than that of (\(E\))-\(\beta\)-damascenone because the compounds have higher sensory threshold values (Table S3). In this study, the chemical characterization of the aroma of 'Marselan' wine included linalool, (\(E\))-\(\beta\)-damascenone, and ethyl esters of C2-C6, while the aroma of the 'Merlot' wine was characterized by diethyl  
Figure 3: Comparison of aroma profiles based on aroma compounds with OAV > 0.1 at the end of maloalactic fermentation and 12-month bottle storage. (**A**) orthogonal partial least squares-discriminant analysis (OPLS–DA) model; (**B**) loading patterns of ‘Marselan’ and ‘Merlot’ wines; (**C**) number of aroma compounds with OAV > 0.1; (**D**) radar chart based on the aroma descriptors of aroma compounds with OAV > 0.1.  
succinate, and ethyl or isoamyl esters of C8-C12 (ethyl hexadecanoate, ethyl laurate, ethyl caprate and ethyl caprylate). Figure 3D displays a radar chart of the odor descriptors based on the compounds with OVA > 0.1. The intensity of floral and honey-like aromas was more pronounced at the 'MLF end' stage in comparison to the'm12' stage, with little difference in the other aromas between the two stages. It is proposed that the discrepancy in the strength of floral and honey-like aromas between the two stages was predominantly attributable to the concentration of (_E_)-\(\beta\)-damascenone (Figure 3B). The fruity aroma of the wine remained consistent throughout the bottle storage period.