## 1 Introduction  
Wine is composed of non-volatile and volatile chemical components, which are responsible for important oenological and sensory characteristics. Among them, polyphenols (PPhs) and volatile organic compounds (VOCs) are responsible for two of the main characteristics in defining complexity and quality of red wines and for the two main intrinsic drivers of red wine consumers' purchasing decisions: astringency and aroma [1; 2; 3; 4; 5; 6; 7; 8]. Wine polyphenols are represented by non-flavonoids (i.e., small molecules such as benzoic and cinnamic acids) and flavonoids (i.e., flavan-3-ols, flavonoids and anthocyanins) compounds. Among them, flavan-3-ols monomers [(+)-catechin and (-)-epicatechin], their oligomers and polymers (usually divided in condensed tannins or proanthocyanidins), and hydrolysate tannins (non-flavonoids polymers) are the most abundant in wine [9]. Condensed tannins are extracted from grapes and then modified during winemaking and aging processes [10]. Hydroysable tannins are extracted from oak barrels or chips during aging or added as enological tannins during winemaking processes [11]. The enenological interest in polyphenols is multifactorial, as they are responsible for wine color and its stability, for wine longevity thanks to their antioxidant activity, and for wine's oral characteristics. The direct contribution of tannins to major oral sensations such as astringency and bitterness has been reviewed recently [12]. Being able to interact and precipitate proteins by forming noncovalent complexes, mostly correlated to conformationally accessible hydrophobic regions of both molecules [13; 14; 15], the interaction between astringent agents (i.e., tannins) and salivary proteins has been proposed as one of the main phenomena in explaining wine astringency perception. Astringency is a complex sensation that involves several mechanisms. Initial steps imply a face-to-face stacking between the aromatic groups of polyphenols and the carbon-hydrogen skeleton of the pyranic rings of condensed tannins with surface-exposed amino acid residues of salivary proteins. These complexes, in subsequent aggregation and precipitation steps, cause a drying and grainy sensation in the mouth that decreases salivary lubrication between oral tissues and increases friction in the oral cavity [8; 16; 17; 18; 19; 20; 21; 22; 23]. This tactile nature of astringency has been investigated since 1954 [16]. Astringency has also been defined as a trigeminal sensation, since some phenolics are able to activate mechanosensors of somatosensory nerves located in the mouth and trigeminal nerve [24; 25; 26; 27]. In addition to astringency, even if information is scarce [12], there is scientific evidence showing that polyphenols can be additionally responsible for the perception of bitterness in wine [8; 28; 29; 30; 31; 32]. (Epi)catechin monomers are more bitter than dimers (procyanidins B3 more bitter than B4, and B6) and trimers (trimers C1 and C2) [29]. Recent results have suggested that several phenolic compounds, such as pentagalloylglucose hydrolysis, (-)-epicatechin, procyanidin trimer C2, procyanidin B2-3-O-gallate, and some ellagitannins activate bitter taste receptors [31; 32]. A prioristically, astringency, and bitterness represent repulsive sensations for consumers, but when well balanced with the other oral sensations, they can add structure/body and persistence to red wines [33] and be perceived as strongly linked to its quality [6]. More than 800 VOCs have been identified in wines, with a concentration range varying from hundreds of mg/L to ug/L or ng/L levels [34]. However, only some of them work as odor-active molecules, mainly in concentrations above their sensory perception threshold but also because of synergistic or masking effects at peri/sub-threshold levels [35; 36; 37; 38; 39; 40].