## 3 Results and Discussion
### Volatile Profile  
Figure 2A shows the total amount of the different volatile compounds grouped by chemical families. As can be seen, neither KT nor KTS appeared to significantly affect the overall concentrations of the main classes of compounds. When individually considered, however, among alcohols, slight but significant impacts were found on n-butanol and n-hexanol contents due to KT and KTS respectively (Table A1). For n-hexanol, previous results reported analogous reductions after fining with solid chitosan [38; 39] added at higher doses (1 g/L). Solubilization of chitosan (KTS) may be hypothesized to increase specific surface, leading to a higher absorption capacity. Regarding esters, it is noteworthy that both chitosan treatments resulted in a lower content of ethyl cinnamate (Appendix A, Table A1). This trend appears to be directly correlated to the resultsof Section 3.2. Structural similarity between ethyl cinnamate and cinnamic acid leads to analogous absorption of the ester onto chitosan surface giving rise to the decrease of its concentration in the wine. According with previous studies [39; 40] foranic compounds, mainly coming from Maillard and Strecker reactions between sugars and amino acids, were found at higher concentrations after chitosan treatments (Figure 2A). This trend, as already investigated by [PERSON] and co-workers [40], is correlated to the presence of amine groups on chitosan backbone that could promote Maillard and Strecker reactions by reacting with wine metabolites such as residual sugars even if, according to those authors, the formation of these compounds mainly occurs after longer storage period. To further evaluate the effects of chitosan on wine aroma, a subset of samples was added of volatile phenols, to simulate a \"Brett\" contamination, and treated with KT and KTS for 7 days. Figure 2B reveals that powdered chitosan (KT) was able to decrease 4-EP and 4-EG by 10 and 40 \(\upmu\)g/L respectively while higher performance was achieved with pre-dissolved chitosan (KTS), with reductions of 55 \(\upmu\)g/L and 45 \(\upmu\)g/L respectively. This different behavior may be linked to the higher specific surface induced by solubilization, promoting absorption capability of KTS toward volatile phenols. Interestingly, both treatments showed a greater effect for 4-EG suggesting that the presence of polar methoxy group on 4-EG could stabilize the interactions with the polysaccharide leading to an increased absorption. These results were in contrast with those obtained by [PERSON] and co-workers [10] where the total amount of volatile phenols was not significantly decreased in red wines but rather in the headspace concentration. This may be due to the fivefold higher dose of chitosan applied in our experiments revealing a dose dependent interaction with volatile phenols. Moreover, higher deacetylation degree used in our treatments seemed to increase chitosan performance, in accordance with results of [PERSON] [9] because of the greater presence of amine (NH\({}_{2}\)) groups of glucosamine units to interact with volatile phenols. However, it should be pointed out that 4-EP and 4-EG removal was limited, and remaining amounts in red wines were still substantially over the perception threshold (400 and 150 \(\upmu\)g/L respectively [14]). According to this evidence chitosan could only be proposed as a remediating treatment for red wines with a low level of contamination of volatile phenols, potentially useful to bring their contents below  
Figure 1: HPLC-DAD chromatogram of phenolic compounds adsorbed onto chitosan surface. the olfactory threshold. This result substantiates the cited findings [9; 10; 41] whereby chitosan was found to preferentially reduce the concentration of volatile phenols in the bottle headspace rather than in the wine itself.