## 2 Results
### Effect of Phenolic Compounds on Aroma Volatility in Wines with Different Oral Components
However, Figure 3c shows a higher release of this odorant in the systems with polyphenols, and mainly when they were supplemented with phenolic extracts. To explain this, one possible hypothesis can be related to the capacity of certain polyphenols to inhibit some salivary enzymatic activities (\(\alpha\)-amylases, carboxylesterases) [41; 42; 43; 44]. It has been demonstrated that human saliva can metabolize carboxylic esters, producing the corresponding carboxylic acids [23; 28]. As previously described, the large difference in ethyl hexanoate volatility between wine with AS and HS has been associated with the hydrolysis of this compound by esterase enzymes (Figure 1c). However, this transformation should not happen if human saliva enzymes are inactivated [28]. Therefore, it is plausible to think that the higher release of this odorant in the wines with HS and phenolic compounds (Figure 3c) might due to the inhibitory effect of these types of compounds on salivary esterase, reducing the transformation of ethyl hexanoate in the corresponding volatile acid, which might happen in the HS systems without polyphenols. Furthermore, both phenolic extracts seemed to have a high inhibitory activity compared to the monomer catechin and the non-flavonoid compound gallic acid, which is in agreement with the higher inhibitory carboxylase capacity of flavonoid-type polyphenols [44]. This funding might also explain previous results [17] in which authors observed a higher decrease in ester release in white wines spiked with human saliva compared to red wines (with flavonoid type polyphenols) when using dynamic headspace conditions. In the case of the wine with AS, a very similar headspace amount of ethyl hexanoate was found in the control wine compared to the wine with phenolic compounds (Figure 3c). However, a significant increase of aroma volatility produced by gallic acid and a significant decrease produced by the addition of RWE was also observed. The addition of a polar compound such as gallic acid might have modified the wine polarity, decreasing the solubility of ethyl hexanoate, which could now be better released to the head space. On the contrary, the formation of weak hydrophobic interactions between a hydrophobic odorant compound and anthocyanin type compounds [5] could reduce the volatility of ethyl hexanoate. Similarly to what happened for wines with AS, in the wines with BC gallic acid increased the volatility of ethyl hexanoate (Figure 3c), while the two phenolic extracts and mainly GSE decreased it, which is in agreement with the previously described hydrophobic interactions. However, the addition of catechin did not reduce ethyl hexanoate volatility, and even produced a slight increase (Figure 3c). Finally, phenolic compounds also affected the volatility of \(\beta\)-ionone in the wines with HS and BC, but not in the wines with AS (Figure 3d). The latter also exhibited the highest values of \(\beta\)-ionone in the headspace. This shows a higher interaction of this volatile compound with polyphenols in the wines with HS and BC compared to those with AS. In both wine types, the addition of phenolic compounds provoked practically the same effect on \(\beta\)-ionone volatility. For instance, the addition of gallic acid produced an enhancement in the volatility of this odorant compound compared to the control wine (above 40% increase). This salting out effect could be related to the reduction in solubility when a highly polar phenolic acid is added into the wine, as also happened for ethyl hexanoate. Since \(\beta\)-ionone is more hydrophobic than ethyl hexanoate, this effect is larger for the former. In presence of flavonoids, a reduction (of above 20% compared to the control) of the amount of \(\beta\)-ionone in the headspace was evidenced in both wine types (with HS and BC) (Figure 3d). Previous works have shown than in the presence of human saliva, it is possible the formation of complexes involving phenolic compounds and salivary proteins is able to encapsulate mainly hydrophobic compounds [18].