# Correlations Between Phenolic Composition and Perceived Astringency of Wines
## 3 Results and Discussion
### Correlations between Astringent Attributes and Perceived Astringency  
Figure 2 shows the relationships between the astringent attributes and perceived astringency. The TPC and the PTC showed strong positive correlations with perceived astringency with coefficients of 0.7934 (\(p<0.0004\)) and 0.7770 (\(p<0.0006\)), respectively. These results are consistent with the previous report by [PERSON] et al. [26] in which the perceived astringency of wines was significantly correlated with the total polyphenol index and protein-precipitable proanthocyanidins. The PAC showed a moderate positive correlation with perceived astringency with a coefficient of 0.6635, which was lower than that of the PTC despite their similar phenolic compositions. Our results were in agreement with [PERSON] et al. [11] who compared four different estimation methods (BSA precipitation, methylcellulose precipitation, Bate-Smith assay and vanillin assay) for proanthocyanidin quantification and evaluated their relationships with perceived astringency and found higher correlation coefficient values in the precipitation methods (BSA and methylcellulose precipitation) than in the colorimetric methods (Bate-Smith and vanillin assay). The higher correlation coefficient value in the PTC compared with the PAC was most likely due to differences in the astringent intensity between the polymeric tannins and the monomeric ones. Many existing studies have suggested that the sensation of astringency is a tactile stimulation rather than one of taste or flavor.  
Although the mechanism behind astringent sensation is not fully understood, the widely accepted principle is that polyphenols bind and precipitate proline-rich salivary proteins (PRPs) through hydrogen bonds and hydrophobic interactions. The precipitation of PRPs reduces the lubricating ability of saliva by decreasing viscosity and increasing friction. In this context, the astringent sensation  
Figure 3: Plots of the correlations between the TPC and the PAC, the TPC and the PTC, the TPC and the TAC, the PAC and the PTC, the PAC and the PAC and the TAC and the TAC and the PTC and the TAC.  
associated with drinking wine is believed to be primarily governed by large molecular tannins such as polymeric proanthocyanidins, which contain a lot of hydrophobic residues and hydroxyl groups. The hydrophobic residues and hydroxyl groups in proanthocyanidins increase their binding affinity to proteins by enhancing intermolecular hydrophobic interactions and hydrogen bonds. Moreover, hydrolysable tannins, consisting of carbohydrates esterified with phenolic acids such as gallic acids or ellagic acids, were found to contribute to the astringent sensation as indicated by the results of the coefficients between perceived astringency and the PTC (Figure 2) and between the PAC and the PTC (Figure 3).  
The TAC was found to be weakly correlated with perceived astringency (\(r=0.3675\), \(p>0.05\)). However, this result was not reliable because the correlation between the TAC and perceived astringency was not statistically significant. According to previous reports, anthocyanins themselves do not seem to contribute to the perceived astringency of wines but rather affect astringency indirectly by forming polymeric pigments [27; 28]. [PERSON] et al. [27] noted that anthocyanins reacted with tannins directly to form new polymeric pigments during the fermentation and storage of wines. The resulting incorporation of anthocyanins into the tannin structure could decrease perceived astringency.