# Impact of Chitosan-Genipin Films on Volatile Profile of Wine along Storage
## 3 Results and Discussion
### Volatile Compounds Retention Capacity of Chitosan-Genipin Films in Wine Model Solutions  
To assess if Ch-Ge films can have specific interactions with wine volatile compounds, assays were designed using wine model solutions containing individual representative compounds of carboxylic acids (hexanoic acid), esters (ethyl acetate and ethyl hexanoate), aldehydes (hexanal and benzaldehyde), ketones (octan-3-one), and alcohols (hexanol). These compounds were selected considering their different functional groups with carbon chains ranging from C4 to C8. The content of each volatile compound in the vapour phase, expressed as mg/L, was determined along at least 4 h, using as reference wine model solutions without Ch-Ge films (Figure 3). For ethyl hexanoate and hexanoic acid, experiments were also performed using different proportion of Ch-Ge films for the same volume of solution.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Wine Model Solution**} & \multirow{2}{*}{**Time (Days)**} & \multicolumn{2}{c}{**[Maillard Volatile Compounds] (mg/L)**} \\ \cline{3-4}  & & **Furfural 1 **} & \multicolumn{2}{c}{**Phenylacetaldehyde **} & \multicolumn{2}{c}{**Benzaldehyde **} \\ \hline Ara + Gro & 36 & * & * & * \\ Ara + Ge & 120 & * & * & * \\ Ara + Ge & 36 & * & * & * \\ Phe + Gro & 120 & * & * & * \\  & 36 & * & 7.5 \(\times\) 1.0 & 0.02 \(\times\) 0.01 \\ Phe + Ge & 120 & * & 62.6 \(\times\) 6.0 & 0.18 \(\times\) 0.01 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Maillard volatile compounds formation in wine model solution containing arabin (Ara) or phenylalanine (Phe) in the presence of glycerol (Gro) and genipin (Ge), the components of chitosan-genipin films, at room temperature in the dark during 36 and 120 days.  
It is possible to observe for ethyl hexanoate and hexanoic acid that their amount decreased along time. After 4 h, the solutions containing 0.5 cm\({}^{2}\) of Ch-Ge film presented 17% and 19% less when compared to reference solutions of ethyl hexanoate and hexanoic acid, respectively. This decrease was even higher when 1 cm\({}^{2}\) and 2 cm\({}^{2}\) were used, 35% for ethyl hexanoate and 45% for hexanoic acid, 38% for ethyl hexanoate and 54% for hexanoic acid, respectively. A decrease in the presence of film was also observed for octan-3-one (28%) using 2 cm\({}^{2}\) of film along 4 h. However, this was not observed for ethyl acetate and hexanol. The difference between ethyl hexanoate and ethyl acetate may be due to the higher hydrophobicity of the former (log P, 2.83, Table 1) than the later (log P, 0.73), confirming the promotion of hydrophobic interaction between Ch-Ge films and long chain hydrophobic compounds. This property should also explain the decrease observed for octan-3-one (log P, 2.30) after 4 h.  
The higher decrease in wine model solutions of hexanoic acid when compared with hexanol may be related to the negative charges of the acid (pKa, 4.88) that can electrostatically interact with Ch-Ge films positive charges (pKa, 6.5).  
The wine model solutions containing hexanol showed a different behaviour from hexanoic acid and, also, from hexanol. It is observed a 12% decrease in the amount of this aldehyde after 4 h. It is possible that hexanal can react with Ch-Ge film amino groups, forming Schiff bases [38] and originating Amadori compounds. The same behaviour, with a decrease of 16%, was observed for benzaldehyde, in accordance with the data obtained for Ch-Ge films wine model solutions containing Ara.  
Figure 2: Hypothetical pathway leading to formation of phenylacetaldehyde and benzaldehyde from chitosan-genipin films and phenylalanine.