## 4 Discussion
Moreover, production of further compounds such as kaempfer-3-rutinoside, kaempfer-3-glucoside, and free kaempfer, in addition to protocatechuic and 4-hydroxybenzoic acids, was reported [51]. Percentage increments of quercetin in our samples suggest its additional formation pathway, e.g., degradation of quercetin glycosides such as quercetin (quercetin-3-rhammoside), isoquercitrin (quercetin-3-\(\beta\)-D-glucose), and hyperoside (quercetin-3-D-galactoside) contained in buckwheat [12; 64], or hyperoside (predominant), avicularin (quercetin-3-arabinoside), quercetin, isoquercitrin, quercetin 3-xyloside, quercetin-3-O-(6''-\(p\)-counaroyl)-\(\beta\)-galactosidase, and quercetin-3-O-(6''-benzoyl)-\(\beta\)-galactosidase identified in cranberries [26; 65]. Similar to buckwheat, cranberries are an abundant source of flavanols, which occur as monomers, oligomers, and polymers. The fermentation process induces depolymerization, and production of free catechins, catechin esters, and gallic acid [51]. The increase in gallic acid (about 34.3-134.9%) observed in our experiment is in accordance with the above-mentioned results. Anthocyanin glucoside metabolism comprises deglycosylation into corresponding aglycones followed by feasible ring fission. Thus, the predominant anthocyanins in cranberry--cyanidin, malvidin, delphinidin, and peonidin--can be converted into protocatechuic, syringic, gallic, and vanillic acid, respectively [28; 51]. This can be considered to be one of the mechanisms leading to the increase in protocatechuic, gallic, and vanillic acids in our fermented products. The published literature also reported condensation reactions between flavanols and anthocyanins to form an anthocyanin-flavanol complex [15]. Transformation of vanillic acid into protocatechuic acid and vanillyl alcohol, and of syringic acid into syringaldehyde and syringol, was described [51]. Correlation analysis was undertaken for the evaluation of the linear association between the analyzed parameters. As concluded from Table S1 (see Supplementary Materials), positive strong correlations were observed between total phenolic content, total flavonoid content, rutin content, and antioxidant activity of the studied mashes (r = 0.819-0.957). Moreover, positive strong correlations were also found between total phenolic and flavonoid content, gallic acid, rutin, and quercetin content (r = 0.810-0.969), caffeic acid and quercetin content (r = 0.929), gallic acid and caffeic acid (r = 0.896), gallic acid and quercetin (r = 0.948), and quercetin, rutin, and total flavonoid content (r = 0.841, r = 0.915). The results of the PCA showed that the three principal components (PC), which accounted together for 90.8% of the total variation (Figure 2), were extracted. PC1 explained 60.9% of the total variation of the studied data and was related to variables flavonoid content, phenolic content, phenolic and flavonoid compounds, and antioxidant activity. PC2 and PC3 explained 20.9% and 9.1% of the total variation, respectively, and mainly reflected the contribution of the variables \(p\)-coumaric and syrigenic acids (PC2) and protocatechuic (Figure 3). The visualization score plot of samples in the coordinates of PC1 and PC2 with the distribution of samples on the plane of principal components is presented in Figure 4.  
PCA divided the samples into three groups according to the applied raw materials for recipe formulation: unflavored water- or milk-based mashes (samples CP0-CP14d, CR0-CR14d, DP0-DP14d, and DR0-DR14d) characterized by the lowest content of total phenolics and total flavonoids and antioxidant activity; milk-based cranberry mashes (BP0-BP14d and BR0-BR14d) characterized by the lowest content of \(p\)-coumaric acid; and water-based cranberry mashes (AP0-AP14d and AR0-AR14d) characterized by the highest content of total phenolics and total flavonoids. In addition, PCA also differentiated groups of mashes with or without the addition of cranberries (Figure 4). By comparison, PCA did not separate the mashes based on the added lactic acid bacteria.