## 6 Conclusions and Future Perspectives  
Wine VOCs-PPhs interactions and their effects on aromas release, headspace partitioning, and sensory perception represent an actual research topic in oenology. Even if some molecular insights at the base of these interactions (\(\pi\)-\(\pi\) interaction and hydrogen bonding) and the importance of VOCs and PPhs hydrophobicity have been proposed around 20 years ago, the mechanisms and the effects of these interactions are still unclear. Results of studies conducted using a variety of methods, detection modes, solutions or wines, tannin additions, or manipulation of VOC concentrations have been seen to be very different, contradictory, or difficult to interpret Moreover, results from orthonasal and retronasal studies show different behaviors, suggesting that oral factors, such as saliva, can affect the interactions. Regarding orthonasal conditions, while for some VOCs chemical classes (e.g., terpenoids, esters, volatile phenols, oxygen heterocycles), it was possible to extrapolate a trend, for others (e.g., alcohols and acids), the poor data available made it difficult to draw a coherent conclusion on phenolic compounds effects on their release. To summarize, the release of all the tested terpenoids decreases at increasing tannin concentrations. For esters, around 2.85 seemed to be a cut-off log\(P\) value: esters characterized by lower logPs diminished at smaller PPhs levels, while they were raised at higher ones, suggesting that for poorly hydrophobic esters, there is the prevalence of retention phenomena at low PPhs concentrations and the prevalence of salting-out effects at higher PPhs concentrations. Conversely, the release of esters characterized by higher logPs, except for ethyl octanoate, decreased independently from the PPhs level, suggesting that hydrophobicity represents the main driving force of highly hydrophobic esters release. Except for guaia-col and eugenol, the release of volatile phenols (e.g., 4-ethylphenol and 4-ethylguaiaicol) was essentially reduced by PPhs. At increasing tannins concentrations, oxygen heterocycles VOCs with log\(P\) values higher than 1 (e.g., \(\gamma\)-nonalactone, trans-whiskey lactone, and cis-whiskey lactone), show a decrease in volatility. To the contrary, VOCs with lower log\(P\) values (i.e., 5-methyl furfural), independently from the matrix type, have shown a \"salting-out\" effect. Globally, the observed trends seem to suggest that in orthonasal conditions, for VOCs with a greater hydrophilic character, an increase in PPhs determines a greater release (salting-out), which is probably because this increase reduces the solvating capacity that the water molecules have toward VOCs. On the contrary, VOCs with a greater hydrophobic character are more retained at increasing PPhs concentration, likely in reason of hydrophobic intermolecular interactions occurring between them. Considering retronasal conditions, it has been observed that in the presence of phenolic compounds, some salivary enzymatic activities may be inhibited (e.g., carboxyl esterase), thus leading to a lower hydrolysis of some VOCs (e.g., esters) in solutions and, consequently, to a higher release. Moreover, phenolic compounds have shown to strongly interact with mucin, \"competing\" with aromas in their interaction with saliva and resulting in some VOCs being characterized by a lower decrease in volatility. Finally, in the presence of tannins, some VOCs, for their ability to participate in the formation of large complexes with salivary proteins and wine carbohydrates, might be encapsulated, leading to a lower retronasal release.