## 5 Polyphenols Effects on Aromas Sensory Perception  
Few experiments have been conducted to measure the sensory impact of polyphenols on aromas perception in orthonasal and retronasal conditions.  
In orthonasal conditions, [PERSON] and co-workers [117] investigated the effects of three polyphenols naturally present in white wines on the perception of four key aroma compounds from a Sauvignon Blanc wine. Their results showed that the perception of isobutyl methylpyrazine and ethyl decanoate was suppressed by catechin, caffe acid, and somehow by quercetin or its degradation products. Regarding the two former phenolic compounds, noncovalent bonds (\(\pi\)-\(\pi\) interaction and hydrogen bonding) between their large-OH groups and the aroma compound might have reduced its perception [51; 52]. The perception of 3-mercaptoethanol (described as passionfruit skin/stalk) was suppressed when catechin and quercetin were added, while it was enhanced by caffe acid. 3-Mercaptohexyl acetate was the least affected volatile, suggesting that the acetate group was less suitable to interact with phenolics compared to the indoxyl. Considering red wine aroma perception in orthonasal conditions, some authors have found that in wines characterized by high polyphenols concentrations (5.4-7.2 g/L), the intensity of perceived fruity, citrus, strawberry, cooked fruit, and floral odors was significantly lower compared to wines with low polyphenols concentrations (1.4-3.2 g/L). A tendency, even if not significant, to the accentuation of spicy, herbaceous, and sweet pepper notes was also observed. However, neither changes in headspace (HS-SPME-GC-MS analyses) nor in matrix concentration (physicochemical composition) showed results that were significantly related to the relative changes in sensory intensity [118].  
In retronasal conditions and focusing on PPhs effects on the prolonged aroma release, a sensory study conducted on a Syrah wine adjusted to two concentrations of ethanol and tannins has pointed out that the duration (length in mouth) of bell pepper flavor (due to the presence of 3-isobutyl-2-methoxyyrazine) was longer at higher tannin concentrations. A possible explanation could be found in a change in release kinetic: the formation of 3-isobutyl-2-methoxyyrazine-tannins complexes [52; 53], which could have resulted in this aroma compound being retained in solution, yielding to a more gradual release of its bell pepper flavor over time [119]. Finally, in the same study cited above [101], a sensory descriptive analysis was performed to compare intra-oral SPME data with sensory assessments. The results showed that wines added with phenolic extracts exhibited lower retronasal intensity for the attributes \"banana\" and \"apple\", which are aromatic notes associated with isoamyl acetate and ethyl hexanoate. At the contrary, the attribute \"honey\", which is correlated to \(\beta\)-phenylethanol, was scored slightly higher in the wines with phenolic extracts, while the attribute \"chemical\" correlated to guaiacol--however, without a relationship to a higher oral release of this latter VOC. The authors suggested that the phenolic extracts that were tested might exert an effect on the prolonged aroma release.  
This seems an interesting research perspective to approach by means of dynamic sensory methods coupled with real-time instrumental techniques to test over time if polyphenols might induce a modification on the long-lasting aroma perception of aroma attributes.