## 2 Results and Discussion
### Volatile Composition of Viura Wines Treated with PS extracts and CM  
Table 1 shows the concentration of individual volatile compounds and volatile families of Viura wines treated with the PS extracts and CM after one month (T1) and twelve months (T12) of bottling. Table 2 shows the OAV values, odor thresholds, and descriptors [26; 27; 28; 29; 30] of the volatile compounds with OAV \(>\) 0.2. Twenty-nine volatile compounds were detected and organized into seven different chemical families: higher alcohols, with 1-propanol, isobutanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and 2-phenylethyll alcohol; C6 alcohols, represented by 1-hexanol, \(E\)-3-hexen-1-ol, Z-3-hexen-1-ol, and benzyl alcohol; ethyl esters, with ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, ethyl-2-methylbutyrate, ethyl isovalerate, and ethyl lactate; acetates, comprising propyl acetate, isobutyl acetate, isoamyl acetate, hexyl acetate, and \(\beta\)-phenethyl acetate; volatile acids, represented by isovaleric acid, hexanoic acid, octanoic acid, and decanoic acid; phenol volatiles, comprising 4-vinylguaicol and 4-vinylphenol; terpen, formed by linalool and \(\alpha\)-terpineol. The one-way ANOVA results revealed that the addition of the PS fractions significantly affected the volatile contents of Viura samples both after one month and twelve months of bottling (T1 and T12, respectively). Higher alcohols were the major chemical family in Viura wines. The use of PS extracts did not produce differences in the content of total higher alcohols after one month of bottling (T1). Only 1-propanol and isobutanol showed significant differences, but both showed OAV values below their odor thresholds (Table 2) and did not contribute to the flavor of the wine. These findings were consistent with those obtained by our research group, who observed that the addition of RG-II-rich extracts and inactivated commercial yeasts rich in MP did not modify the content of higher alcohols in _Albillo_ and _Verdejo_ wines [16]. However, after twelve months of bottling (T12), the addition of PS extracts reduced the content of total higher alcohols compared to the control wine. In fact, grape-derived PS extracts (WPP and DWRP), rich in RG-II and minor PRAG, reduced the content of higher alcohols more effectively than CM rich in MP. The effect of wine PS on wine volatile compounds has been analyzed by several authors, showing contradictory results on many occasions [6]. Many studies are carried out in model systems and not in real wine samples, and PSs are described to affect aroma volatility, either indirectly \"by changing the viscosity of the media\" or by direct interaction with volatile compounds, with these interactions being dependent on the physico-chemical structure of the volatile molecules [5] and probably on the physico-chemical composition of the PS involved. Therefore, it seems that the protein part of the PS, such as in MP or PRAG polysaccharides, affects to a greater extent the glycosidic parts regarding the interactions with volatile compounds [13; 31], which are mainly hydrophobic interactions and hydrogen binding. Furanic compounds, volatile phenols and aldehydes, and cyclic alcohols (2-phenyl ethanol), all with low hydrophobicity and a flat structure, are retained by the MP since \(\pi\)-\(\pi\) stacking occurs between the aromatic/furanic ring of the compounds and the protein part of the mannoprotein. On the other hand, MP, PRAG, and RG-II can form stable colloids in solution with tannins and protein aggregates [32]. Hence, the reduction in some aromatic compounds could also be attributed to an indirect effect of PS. Higher alcohols would precipitate by the formation of haze and by interactions with wine proteins and phenolics, resulting in hydrophobic interactions, hydrogen bonds, and/or \(\pi\)-\(\pi\) stacking [33; 34]; however, the indirect interactions are mainly theorical and need to be contrasted in future studies [35].