## 2 Results and Discussion
### Sensory and Chemical Profiles of Monovarietal Wines
Based on the PCA result (Figure 2a), '82' samples are located more closely to CF wine than '64' samples, indicating that the volatile profile had great correlation with proportions. In addition, the distribution of '82' and '64' samples became more dispersed during bottle  
Figure 1: Sensory characteristics (**a**) and volatile profiles (**b**) of four monovarietal wines. CF, CS, MA, and PV refer to _Vitis vinifera_ L. cv Cabernet Franc, Cabernet Sauvignon, Marselan, and Petit Verdot wines, respectively. The concentration of different compound categories in (**b**) is in units of \(\upmu\)g/L except * MPs is in units of ng/L. Detailed information of volatiles is listed in Table S1. aging, especially in the binary blending samples CFC (CF wines \(\times\) CS wines) and CFM (CF wines \(\times\) MA wines), namely, CFC82 vs. CFC64 and CFM82 vs. CFM64. In other words, the blending procedure could not only change the concentration of chemicals but also influenced the evolution of volatiles during aging to lead to more differentiated volatile profiles between different blending proportions after six-month bottle aging. However, compared to the factor of blending proportion, the blending type was a more prominent factor resulting in greater difference. To be more specific, CFP samples (CF wines \(\times\) PV wines) were mainly located in the first quadrant where PC1 and PC2 were both positive, while CF wines and the other two blending types could not be separated by quadrants, suggesting that the volatile profile in CFP samples differed more from CF wines than the other two blending types. According to the scattering loading biplot (Figure 2b), three MPs were located in the inner ellipse in biplot of PCA, suggesting that the level of MPs was not the main factor that determined the difference between CF wines and blending samples. As for volatile compounds selected in the outermost ellipse to determine the PCA model, C6/C9 alcohols were located in the first quadrant, representing higher concentrations in CFP samples, which was accordant with the characteristic of PV counterpart wines (Figure 1b). Acetates were distributed in the quadrants where PC2 was positive, presenting at higher concentrations in samples of 0 M and CFP blending type. The distributions of ethyl esters and other esters were mainly gathered in the second and fourth quadrants, exhibiting higher concentrations in samples of CFC and CFM blending types. In other words, the regulation of volatile profile in blending wines was mostly dependent on characteristics of different counterpart wines and the differences between blending types could be maintained after six-month bottle aging. However, the sensory differences between blending types had some variation against the corresponding counterpart wines, which were visualized by clustered heatmap every three-month interval after bottling through sensory experiments (Figure 3). According to the results of quantitative descriptive analysis, the intensities in 'green pepper' and 'herbaceous' notes diminished in all binary blending samples comparing to CF base wines. In the blending types of CFM and CFP, CFM82 and CFP82 samples had higher intensities in 'green pepper' notes than CFM64 and CFP64 samples, which was in accordance with the concentration of IBMP (Figure 4). Although CFC samples had higher concentration of IBMP than CFM and CFP samples, CFC samples could be mostly distinguished from CF base wines with lower intensity of 'green pepper' and 'herbaceous' aromas. In addition, CFP samples did not exhibit prominent high intensity of 'tropical fruit', which was not  
Figure 2: Principal component analysis of volatile compounds in CF wines and blending samples. (**a**) Score plot for wine sample differentiation at three-month intervals during six-month bottle aging. CFC, CFM, and CFP refer to binary blending samples of CF wines \(\times\) CS wines, CF wines \(\times\) MA wines, and CF wines \(\times\) PV wines, respectively. The numbers 82 and 64 refer to CF wines accounted for 80% and 60%.