## 2 Results and Discussion
### Proanthocyanins of Viura Wines Treated with PS Extracts and CM  
Table 4 shows the total proanthocyanidin (PA) content and mean degree of polymerization (mDP), as well as the percentages of epicatechin, catechin, and epicatechin gallate terminal subunits in Viura wines treated with the PS extracts and CM at T1 and T12. The PA content was similar to that described by [46] in Viura wines. No statistically significant differences were obtained for total PA concentration at T1. The % of catechin, the primary terminal subunit in the grape skin [47], and epicatechin was higher in the wines treated with the PS extracts, except for % (+) catechin in the WPP wine. The mDP, which is an indicator of the wine sensory properties of bitterness and astringency [48], significantly decreased in the wines treated with the grape-derived PS extracts (WPP and DWRP) and CM. After 12 months of bottle aging (T12), the use of both grape-derived PS extracts and CM produced a loss of PA (Table 4). The addition of WPP and DWRP produced a similar reduction in the PA content compared to CM (~22-29%). In the bibliography, a reduction in the wine astringency produced by MP is described due to a precipitation effect. Therefore, the flocculant effect can lead to coaggregation and precipitation of MP-flavanol complexes in wines, and a decrease in flavanols [49; 50; 51]. In the same way, the high content of RG-II dimmer in the WPP and DWRP extracts and its interaction with flavanols to form complexes explains the decrease in PA in the wines. [PERSON] et al. [52] reported that RG-II strongly enhanced the mean apparent diameter of these complexes with time, suggesting co-aggregation between RG-II dimer and tannin. After 12 months of bottling, wines treated with WPP and DWRP had lower contents of PA than control wines, probably due to the size increase and precipitation of the PA-RG-II complexes, corroborating the results obtained by [52]. As observed in T1, the use of grape-derived PS extracts reduced the mDP of PA, obtaining similar effects between DWRP and CM. It can be concluded that the grape-derived PS extracts can potentially reduce the astringency perception since they reduced both the PA content and the mDP of the PA, related to the astringency and bitter sensations [48]. Therefore, these extracts have a good potential to be considered as finning agents to modulate wine astringency and bitterness, which is especially important in white wines with an undesirable excess of bitterness or astringency sensations. \begin{table} \begin{tabular}{c c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**P1**} & \multicolumn{4}{c}{**T1**} & \multicolumn{4}{c}{**T12**} \\ \hline
**Polymeric** & \multicolumn{4}{c}{**C \({}^{\star}\)**} & **WPP \({}^{\star}\)** & **DWRP \({}^{\star}\)** & **CM \({}^{\star}\)** & **F-Value** & **C \({}^{\star}\)** & **WPP \({}^{\star}\)** & **DWRP \({}^{\star}\)** & **CM \({}^{\star}\)** & **F-Value** \\ \hline PA & 60.47 (3.91) & 54.78 (3.33) & 55.45 (0.26) & 49.33 (2.89) & 3.660 (ns) & 45.2 (2.95) b & 35.74 (1.87) a & 34.80 (.95) a & 32.69 (1.83) a & 6.986 \({}^{\star}\) \\ \% CM & 10.40 (2.64) b & 7.23 (2.23) a & 13.07 (1.58) c & 11.07 (1.47) b & 10.695 \({}^{\star}\) & 9.5 (2.32) b & 7.2 (0.12) a & 12.10 (1.32) c & 11.02 (1.32) b & 11.538 \({}^{\star}\) \\ \% Epi & 16.13 (2.09) a & 21.75 (2.97) b & 2.39 (2.79) c & 18.77 (2.36) a & 9.774 & 7.02 (0.95) a & 9.97 (1.39) b & 10.72 (1.24) b & 9.17 (1.13) b & 10.538 \({}^{\star}\) \\ \% Epi-gal & 2.78 (0.31) & 2.69 (0.27) & 2.69 (0.37) & 3.26 (0.59) & 2.729 (ns) & 1.60 (1.11) a & 1.58 (0.10) a & 1.49 (0.13) a & 1.95 (0.22) b & 10.924 \({}^{\star}\) \\ mDP & 2.75 (0.35) c & 2.08 (0.23) b & 1.61 (0.15) a & 1.7 (0.17) a & 174.180 \({}^{\star}\) & 3.22 (0.47) c & 2.37 (0.24) b & 1.62 (0.14) a & 1.68 (0.15) a & 155.70 \({}^{\star}\) \\ \hline \end{tabular}   
* \({}^{\star}\) Main values are shown in (a-3).