## 2 Results
### Effect of Phenolic Compounds on Aroma Volatility in Wines with Different Oral Components
While guaiacol volatility was more similar in the control wine (without polyphenols) than the wines with gallic acid or GSE, in the case of the wines with catechin, a strong reduction of volatility (above 50% compared to the control) was observed. The addition of RWE into the wines with BC produced a salting out effect, and therefore, an increase in guaiacol volatility above 20% compared to the control wine. The different effect of polyphenols on guaiacol volatility in wines spiked with BC compared to wines with AS could be due to the different hydrophobic properties of BC. As said before, the presence at the surface of the oral cells of highly hydrophobic and hydrophilic domains due to the expression of different types of mucin [33] might differently affect the binding of different types of phenolic compounds to BC, which in turn might also affect the interaction with guaiacol. In the case of \(\beta\)-phenyl ethanol, the effect of phenolic compounds was significant in the three types of wines (with HS, AS, and BC) (Figure 3b). In general, in all of them, the addition of these compounds produced a reduction on \(\beta\)-phenyl ethanol volatility compared to the control wine. Only in the case of the wines with HS did the addition of gallic acid provoke a salting out effect. Interestingly, a similar effect (an enhancement of aroma volatility) has been shown in wines with high phenolic acid content when using in-mouth aroma monitoring [38]. In general, the lowest headspace concentration of this odorant was found in the wines spiked with flavonoid type compounds, being the wines with GSE exhibiting the lowest volatility of \(\beta\)-phenyl ethanol. For instance, in wines with BC, the reduction of aroma volatility by adding GSE was about 50% compared to the control (Figure 3b). Considering the relatively low hydrophobicity and the presence of an aromatic ring in the \(\beta\)-phenyl ethanol molecule, the formation of \(\pi\)-\(\pi\) interactions with these flavonoids might also be a plausible explanation for the reduced volatility of this odorant in the presence of these types of polyphenic compounds. A significant effect of polyphenols on ethyl hexanoate volatility considering the three types of wines supplemented with oral components was also found (Figure 3c). On the basis of its _log P_ (hydrophobicity) value (Table 1), this compound can be considered of hydrophobic nature. Interestingly,  
Figure 3: Effect of phenolic compounds (No: without polyphenol, GAc: gallic acid, Cat: catechin, RWE: red wine extract, GSE: grape seed extract) on wine aroma volatility. For each aroma compound, (**a**) Guaiacol, (**b**) \(\beta\)-Phenyllethano, (**c**) Ethyl hexanoate and (**d**) \(\beta\)-Ionone, and type of wine system, different letters on the top of the bars denote significant differences among wines spiked with different polyphenols (\(p<0.05\)) from Tukey test. the effect of each type of polyphenol was very different in the wine with human (HS) or artificial (AS) saliva (Figure 3c). As it can be seen (Figure 3c), in the wine with HS the lowest percentage of headspace release was found in the control wine without polyphenols. In the wines with polyphenols, and mainly in those supplemented with the two phenolic extracts (RWE and GSE), ethyl hexanoate volatility increased above 60% compared to the control wine without polyphenols. Both extracts were mainly composed of anthocyanins and procyanidins, respectively [39; 40], but their effects on ethyl hexanoate volatility were very similar. Previous works have proven the existence of hydrophobic-driven, weak bimolecular aroma-phenolic compound interactions [4]. Additionally, [PERSON] and [PERSON] [5] reported that at pH 3.5 (normal wine pH), malvin, the hemiacetal form of the anthocyanin 3,5 diglucoside, was primarily responsible for aroma interactions. The consequence should be a reduction on aroma volatility, even larger for a relatively high hydrophobic molecule as ethyl hexanoate.