## 3 Results
### Influence of Cluster Thinning and Type of Alcoholic Fermentation on Wine Parameters  
#### 3.4.1. Location M  
Table 1 shows the results of the influence of cluster thinning (CT) and the type of alcoholic fermentation (AF) on the volatile compounds and other wine parameters for location M. The influence of CT on the Merlot variety showed a significant and repeatable year-on-year effect on the increase in the ethyl acetate, volatile acidity, and pH of the wine. In 2020 and 2021, CT increased the pH value of the wine from 3.61 to 3.64 and from 3.60 to 3.65, the volatile acidity of the wines from 0.35 to 0.40 g/L and from 0.29 to 0.35 g/L, and the concentration of ethyl acetate from 54.7 to 70.4 ug/L and from 33.9 to 46.5 ug/L.  
For the IBMP, ethyl dodecanoate, ethyl palmitate, sum of EEFAs, isoamyl acetate, 2-phenethyl acetate, sum of acetates, 1-hexanol, (Z)-3-hexen-1-ol, 1-propanol and TAns parameters, a significant interaction between CT and vintage was confirmed, with CT causing an increase in one year and a decrease in another year in their concentrations. It is also evident that the vintage influenced more significant differences in the levels of the individual compounds than CT itself, as significantly higher levels of ethanol, 3 MH, and the sum of acetates and other alcohols than ethanol and 3 MH and significantly lower levels of IBMP, the sum of EEFAs, diethyl succinate, \(\gamma\)-butyrolactone, and ethyl acetate were quantified in the 2021 wines (Table 1).  
The influence of the AF type on the Merlot variety at location M was demonstrated in two consecutive years, as spontaneous AF had a significant and reproducible effect on the decrease in the ethyl decanoate content and the increase in the sum of acetates and 2-phenylethanol content (Table 1). In 2020 and 2021, spontaneous AF reduced the content of ethyl decanoate from 52.0 to 36.3 ug/L and from 56.3 to 13.2 ug/L and increased the sum of acetates from 30.0 to 95.3 ug/L and from 43.2 to 70.9 ug/L and the content of 2-phenylethanol from 38.9 to 56.8 mg/L and from 37.6 to 57.6 mg/L (Table 1). For the 3 MHA, 1-propanol, and TP parameters, a significant interaction between the type of AF and the vintage was confirmed. All the other influences depended on the vintage. We found significantly higher levels of 2-phenethyl acetate and 2-methyl-1-propanol, and significantly lower levels of (Z)-3-hexen-1-ol, in the wines from sAF in 2020. This comparison also showed that the vintage triggered more significant differences in the levels of the individual compounds than the type of AF itself (Table 1).  
A PCA was applied to the quantified wine parameters over the two vintages for location M and explained 65.69% of the variation with the first two dimensions (Figure 1). The M-C and M-CT treatments were not separated by the PCA analysis in each experimental year, but principal component (PC) 1 separated both vintages (Figure 1a), with the 2021 vintage M-C and M-CT wines positively associated with ethanol, total acidity, 2 methyl-1-butanol, and benzaldehyde, and the 2020 vintage M-C and M-CT wines positively associated with 4 MMP, 3 MHA, ethyl decanoate, (Z)-3-hexen-1-ol, and TP (Figure 1b).  
Figure 1a also shows that the M-C wines of the sAF (M-C\({}_{\_}\)sAF) differed from the wines of the M-C treatment with inoculated fermentations by PC2 and explained 26.56% of the variation in the dataset. The imposed 95% confidence ellipses showed that significant differences were observed between the M-C\({}_{\_}\)sAF and M-C (with iAF) treatments in both vintages (Figure 1a). The wine VA, ethyl acetate, ethyl dodecanoate, 2-methyl-1-propanol, 2-phenylethanol, 2-phenethyl acetate, and sum of acetates were positively associated with sAF (Figure 1b). It can be assumed that the type of alcoholic fermentation in both vintages at this location had a greater influence on the wine parameters than the yield reduction due to cluster thinning, and that the vintage effect was less pronounced within the type of alcoholic fermentation than within the different crop loads.