## 2 Molecular Insights  
The pioneering research conducted on wine PPhs-VOCs interactions and, consequently, on the effects of polyphenols on aromas release dates to the late 1990s [51]. The authors evaluated the influence of phenolic compounds such as (+)-catechin, epiccatechin, and a highly condensed tannin fraction (extracted from wine) on some linear or aromatic wine aromas with different hydrophobicity, which were added in 10% hydroalcoholic or wine model solutions. A dynamic exponential dilution technique and 1H NMR to probe the interactions at the molecular level were used. General decreases of volatility for isoamyl acetate, ethyl hexanoate, benzaldehyde, and limonene were correlated to increasing concentrations of (+)-catechin (0-12 g/L), with the latter less retained at low catechin concentrations (0-5 g/L). Unlike catechin, the tannin fraction induced a slight decrease of benzaldehyde release and a salting out of limonene with no effect on the two esters, thus suggesting that monomeric or oligomeric/polymeric PPhs can differently impact volatility. At the molecular level, the NMR study focused on aromas-monomeric polyphenols interactions. Similar weak bimolecular bindings were reported for the intermolecular complexation of isoamyl acetate, ethyl hexanoate, and benzaldehyde with catechin. Both catechin and epicatechin showed a higher affinity to benzaldehyde than for 3,5-dimethoxyophenol. Monomers had a higher affinity for benzaldehyde than for themselves. In subsequent work, [PERSON] and collaborators [52], applying \({}^{1}\)H NMR spectroscopy analyses, have explained the supramolecular assembly at the base of specific VOCs-PPhs interactions by noncovalent bonds. The authors have shown that the addition of gallic acid to model solutions containing 2-methylpyrazine, vanillin, or ethyl benzoate has reduced their volatility mostly due to \(\pi\)-\(\pi\) stacking of the galloyl ring of the phenolic compound with the aromatic ring of the odorant molecule, with secondary hydrogen-bonding effects helping in stabilizing the complex and enhancing the specificity, as represented in Figure 1. Moreover, the supramolecular complexation also depends on the structural nature of the VOC, with 2-methylpyrazine and vanillin interacting more strongly than ethyl benzoate. These molecular insights have represented the starting point for further research conducted in the last decades by means of updated approaches/methodologies, and they aimed at understanding how the volatility and sensory perception of wine aromas could be affected by the presence of polyphenols. The two studies cited suggested the hydrophobicity of both PPhs and VOCs as a main driving force in explaining bimolecular aroma-phenolic compound interactions, which were then significantly involved in the modification of VOCs release. Supporting results were obtained by a different approach [53]. The authors prepared model solutions of ethyl benzoate (2 to 16 mg/L in 1% ethanol-water mixture) and 2-methylpyrazine (60 to 300 mg/L in water) and investigated their interactions with gallic acid (10 mM) through HS-SPME/GC-MS and sensory analysis. Their results are aligned to molecular evidence: the addition of gallic acid significantly decreased the headspace partitioning of the two VOCs and their perceived aromatic intensity. The variation in VOCs response to polyphenols depends not only on the concentration or on the chemical characteristics of both VOCs and PPhs but also on other matrix characteristics such as ionic strength and ethanol content. These variables can impact polyphenols' structure, aggregation, solvation, colloidal state [54], and involvement in \"salting-out\" and/or hydrophobic phenomena that are likely to impact their interactions with VOCs. All the mentioned factors may affect how PPhs interact with VOCs and consequently, their release and perception.