# Impact of Chitosan-Genipin Films on Volatile Profile of Wine along Storage
## 3 Results and Discussion
### Impact of Chitosan-Genipin Films on Wine Volatile Composition  
The volatile composition of white and red wines that were in contact with chitosan-genipin (Ch-Ge) films along 2 and 8 months is represented by two heatmaps, one with the 177 compounds identified in white wines (WW, Figure 4) and another with the 206 compounds identified in red wines (RW, Figure 5). After 8 months, esters, acids, and ketones tend to decrease their concentration in both white and red wines (blue colour), whereas furans and aldehydes tend to increase (red colour). The decrease in ketones (as heptan-2-one and nonan-2-one) and the increase in furans (furfural) and aldehydes (benzaldehyde) were observed in a previous work for white wine treated with Ch-Ge films when compared with untreated wines [21]. Nevertheless, these variations were not observed for all compounds in the same chemical family. The detailed information about the volatile compounds identified by HS-SPME/GC \(\times\) GC--ToFMS in white and red wines is provided in the Supplementary Materials (Table S1). Grouping the 139 compounds identified in all wines according to their hydrophobicity index, log P, it is possible to observe that the decrease after 8 months occurred mainly due to the non-polar (log P \(\geq\) 2.3) compounds. The decrease was 1.65-fold lower (\(p\) < 0.05) for white wine (Figure 6), which corresponded to 32% of the area of the 78 compounds, and 1.87-fold lower (\(p\) < 0.05) for red wine, corresponding to 15%. Although the total GC \(\times\) GC peak areas for these 139 compounds were similar for white and red wines, 9.4 \(\times\) 10\({}^{8}\) and 9.1 \(\times\) 10\({}^{8}\), respectively, the non-polar compounds of white wines showed higher GC \(\times\) GC peak areas than those of red wines, 2.0 times for 2 months and 2.3 times for 8 months. Figure 3: Evolution of the volatile compound concentration (mg/L) determined by HS-SPME-GC-FID, in wine model solutions without (���) and with chitosan-genipin films (2 cm\({}^{2}\), 1 cm\({}^{2}\), and 0.5 cm\({}^{2}\) ) at room temperature in dark during 260 min for (**A**) ethyl hexanoate, (**B**) hexanoic acid, (**C**) octan-3-one, (**D**) ethyl acetate, (**E**) hexanol, (**F**) hexanal, and (**G**) benzaldehyde. Nevertheless, the films retention effect was similar in both wines, seeming to be ruled by hydrophobic interactions. Principal component analysis of these datasets (Figure 7) is observed in PC1 (42% of variability) the separation of white (PC1 negative) from red wines (PC1 positive). PC2 (30% of variability) allowed the separation of the wines with longer contact with films (PC2 negative) from those with a shorter contact (PC2 positive). The white wines in contact with the films during 2 months are explained by PC1 negative, with low influence in PC2, whereas the red wines in contact with the film during 2 months are explained by PC2 positive, with low influence in PC1. The loadings plot showed that a large majority of non-polar compounds are represented in PC1 negative and PC2 positive quadrant, evidencing a possible interaction of these compounds with Ch-Ge films along the time of contact. This is even more evident for log P > 4 compounds. Figure 4: Heat map representation corresponding to the 177 volatile compounds of the white wine in contact with chitosan-genipin films during 2 and 8 months. The relative content of each volatile compound is illustrated through a colour scale (from dark blue, minimum, to dark red, maximum). * Significance at \(p\) < 0.05. Detailed data in Table S1. Figure 5: Heat map representation corresponding to the 206 volatile compounds of the red wine in contact with chitosan-genipin films during 2 and 8 months. The relative content of each volatile compound is illustrated through a colour scale (from dark blue, minim, um, to dark red, maximum). * Significance at \(p<0.05\). Detail data in Table S1.