## 3 Results and Discussion
### Contents of Phenolic Compounds in Croatian Wines
#### 3.1.4 Differentiation of the Selected Monovarietal Red and White Wines  
Because of the obvious difference between red and white wines, a separate principal component analysis (PCA) was performed using the data in Tables 3-5. Analysis of the PCA score plot for the monitored values showed that 61.02 and 53.97% of the total variance in the data could be described by F1 and F2 for red and white wines, respectively. Figure 2 shows three well-separated clusters for the red wines studied and a biplot derived from the polyphenic compounds. The Croatian autochthonous wines Plavac Mali (rPD and rPI) and Babic (rBS) form a separate group in the first quadrant. The mentioned differences are mostly due to the different contents of gallic acid, \(p\)-coumaric acid, ferulic acid, catechin, and procyanidin B1 compared to other red wines. Our study supports the results of [PERSON] et al. (2016) and [PERSON] et al. (2011) about the most specific composition of Plavac Mali compared to other Croatian red wines. In this context, we found for the first time the same varietal differences in Babic wine, which is also produced from Croatian autochthonous grape varieties. A group of non-native wines, including Merlot (rMK), Cabernet Sauvignon (rCK), and Syrah (rSK), was also separated. According to F1, this group shows similarity with Croatian autochthonous red wines from the same wine-growing region, and the differences present can be attributed mostly to higher levels of quercetin and rutin compared to Plavac Mali and Babic wines. One of the possible reasons for this difference is the better adaptation of autochthonous species to local conditions and the resulting lower stress, which leads to a lower accumulation of quercetin (Kal  
Although the white wines did not differ as much as the red wines, the multivariate analysis revealed more detailed relationships among them. Figure 3 shows the PCA of the clustering of Croatian white wines and a biplot derived from the polyphenic compounds. In the third quadrant, there is a separate sample of Malvasia Bianca Lunga wine from Northern Dalmatia (wMS), which is significantly different from the other white wines, including wine from the same grape variety (wMA). Compared to other white wines, \(o\)-coumaric acid was detected only in the wMS sample. In addition, wMS also contained significantly lower amounts of caffeic acid and \(p\)-coumaric acid than other white wines. Compared to the wine of the same variety from Southern Dalmatia (wMA), it also had significantly higher levels of gallic acid and procyanidin B2. Possible reasons for this lie not only in the different locations but also in the winemaking process. Namely, wMS was produced using a special technique based on aging on the lees (_sur lie_), which has been shown to correlate positively with gallic acid levels [65]. Proteolytic enzymes released during yeast autolysis could be involved in the hydrolysis of tannins and, consequently, in changes in the composition of polyphenols and the associated sensory characteristics of the wine [66]. Two other wines were also distinguished based on their phenolic profile. Pinot Blanc originating from the Croatian Uplands (wPD) and Chardonnay from Istria (wCR) were distinguished from the other white wines by their high content of catechin. In addition, significantly higher levels of caffeic acid and \(p\)-coumaric acid in wCR (the second quadrant) than in the other white wines contributed to the separation of this sample from the others. Figure 3 shows the similarity between Traminer (wTI), Sauvignon Blanc (wSD), and Rhine Riesling (wRD) from Slavonia and the Croatian Danube according to F2, which is mainly due to the very comparable compositions of phenolic acids, while the distinction from the other white wines is due to the content of gallic acid. The high content of procyanidin B2 in wRD is the reason why it differs from wTi and wSD. Figure 2: Principal component analysis of the clustering of Croatian red wines based on phenolic composition (**A**) and biplot with active variables (**B**).