## 3 Results
### Influence of Cluster Thinning and Type of Alcoholic Fermentation on Wine Parameters
#### 3.4.2 Location B  
Table 2 shows the results of the influence of cluster thinning (CT) and the type of alcoholic fermentation on the volatiles and other wine parameters for location B. The influence of CT on the Merlot variety at this location and in two consecutive years was shown to have a significant and repeatable year-on-year effect on the increase in the ethanol content and pH values. In 2020 and 2021, CT increased the ethanol content from 13.46 to 14.09% vol. and from 15.38 to 15.81% vol. and the pH value of the wine from 3.48 to 3.56 and from 3.65 to 3.70. A significant interaction between CT and vintage was confirmed for the ethyl palmitate, benzyl alcohol, (Z)-3-hexen-1-ol, sum of alcohols and VA. The other influences depended on the vintage; otherwise, a significantly lower content of (Z)-3-hexen-1-ol was found in the CT wines in 2020 and a significantly higher content  
Figure 1: Principal component analyses (PCAs) conducted on the quantified wine parameters for the samples from location M, two vintages (2020, 2021), and for the first two principal components: (**a**) score plot for the first two principal components; ellipses represent 95% confidence intervals for sample groups; M–C—control crop load, M–CT—cluster thinning, both with inoculated alcoholic fermentation; M–C\({}_{\_}\)sAF—control crop load and spontaneous alcoholic fermentation (AF); and (**b**) loadings for the first two principal components; size of the bubbles indicates the importance to the separation of samples for individual variable. of VA, ethyl palmitate, sum of acetates and alcohols, 1-hexanol, 1-propanol and (Z)-3-hexen-1-ol in 2021, together with a trend to significantly lower content of TP, in the CT wines of both vintages (Table 2). It is obvious that here, too, the vintage has triggered more significant differences in the content of the individual compounds than the CT itself, because in 2021, for example, a significantly higher content of ethanol, VA, pH, ethyl butyrate, ethyl dodecanoate, ethyl palmitate and diethyl succinate and significantly lower levels of IBMP, isoamyl acetate, 1-hexanol, benzyl alcohol, (Z)-3-hexen-1-ol and the sum of alcohols compared to the 2020 vintage were found in at least one of the wines from the two crop loads (C or CT) (Table 2). In 2021, spontaneous AF had a significant impact on the decrease in the content of ethanol (from 15.38 to 14.72% vol. ), 3 MH (from 1.305 to 614 ng/L), ethyl butyrate (from 178.7 to 72.9 \(\mu\)g/L), ethyl octanoate (from 232.0 to 86.6 \(\mu\)g/L) and 1-propanol (from 16.2 to 12.8 mg/L), and the the increase in the content of 3 MHA (from 8.09 to 14.66 ng/L), 2-phenethyl acetate (from 34.3 to 54.3 \(\mu\)g/L), sum of acetates (from 37.7 to 58.1 \(\mu\)g/L), 2-methyl-1-propanol (from 49.9 to 72.4 mg/L), ethyl acetate (from 53.8 to 78.5 \(\mu\)g/L), VA (from 0.56 to 0.94 g/L) and pH (from 3.65 to 3.78) (Table 2). A PCA was applied to the quantified wine parameters across two vintages for location B and explained 72.90% of the variation with the first two dimensions (Figure 2). The B-C and B-CT treatments were not separated by the PCA analysis in each experimental year, but PC1 and PC2 separated both vintages (Figure 2a), with the B-C and B-CT wines of the 2021 vintage positively associated with ethanol, 3 MH, ethyl butyrate, 1-butanol, ethyl palmitate, and ethyl dodecanoate, and the B-C and B-CT wines of the 2020 vintage positively associated with IBMP, 4 MMP, 3 MHA, ethyl decanoate, hexyl acetate, isoamyl acetate, 1-hexanol, benzyl alcohol, (Z)-3-hexen-1-ol, 3-methyl-1-butanol, sum of alcohols, and TAns (Figure 2b). Figure 2a also shows that the 2021 B-C wines of the sAF (B-C_sAF 2021) differ from the 2021 wines of the B-C treatment with inoculated fermentations (B-C_iAF 2021) by PC2, which explains 20.36% of the variation in the dataset. However, the imposed 95% confidence ellipses showed no significant differences between treatments B-C_sAF and B-C_iAF 2021 (Figure 2a), but it should be emphasised that at this location, sAF was only performed in 2021.