# Impact of Chitosan-Genipin Films on Volatile Profile of Wine along Storage
## 3 Results and Discussion
### Promotion of Maillard Reactions by Chitosan-Genipin Films in Wine Model Solutions  
The wine model solutions of arabinose (Ara) containing Ch-Ge films showed the formation of furfural, which increased along the 120 days (Figure 1A). However, furfural was not detected in the absence of the films neither in the presence of genipin (Ge) and glycerol (Gro) (Table 2). These results may be explained by the reaction of amino group of chitosan with the aldehyde group of Ara resulting in the furfural formation. This is in accordance with previous studies that showed the reaction of chitosan amino groups with monosaccharides [31; 32] and reducing disaccharides [31; 33], producing brown pigments as final stage products of Maillard reaction. A similar mechanism, where chitosan reacts with fructose at higher temperature and low water activity, explains the mitigation of acrylamide formation by competition of chitosan amino groups with asparagine [34].  
Figure 1: Maillard volatile compounds formation in wine model solutions containing (**A**) arabin (Ara), (**B**) leucine (Leu), and (**C**) phenylalanine (Phe), in the absence () and presence of chitosan-genipin films () at room temperature in the dark during 120 days.  
The wine model solutions of leucine (Leu) containing Ch-Ge films showed the formation of 3-methylbutananal (Figure 1B), possibility resulting from the decarboxylation and oxidative deamination of Leu through a Strecker degradation. The same Strecker degradation mechanism can explain the formation, in wine model solutions containing phenylalanine and Ch-Ge films, of phenylacetaldehyde and benzaldehyde (Figure 1C), the latter explained by the decarboxylation of phenylacetaldehyde (35). For the formation of amino acid Strecker degradation reactions it is necessary the presence of an aldehyde group. Chitosan has, in fact, a carbonyl group at its reducing terminal. As a chitosan with an average of 150 kDa molecular weight was used to prepare the Ch-Ge films, 2 cm\({}^{2}\) of film (Ch, 10 mg) had 0.07 umol of reducing terminals, a value much lower than the amount of Leu (30 umol) and Phe (30 umol) used in these experiments. Although the amount of 3-methylbutananal formed after 120 days (0.08 umol) can be explained by this hypothesis, the amount of benzaldehyde (0.4 umol) cannot, as the amount of Strecker aldehydes formed in the wine model solution containing phenylalanine and Ch-Ge films is 6-fold higher than that explained by the amount of this reducing terminal. Therefore, other components of Ch-Ge film, namely genipin (1.0 umol), which is a dialdehyde, although crosslinked, may still have free aldehyde groups able to be involved in the Strecker degradation of amino acids. To confirm this hypothesis, a wine model solution containing Phe and Ge was analysed. This experiment showed the formation of phenylacetaldehyde and benzaldehyde (Table 2), but not when Phe was in contact with Gro, showing that Ge promotes Strecker degradation. Figure 2 shows the proposed mechanism for the formation of the phenylacetaldehyde and benzaldehyde by Ch-Ge films. The results reported are in accordance with the ability of genipin to react with amino acids for different purposes, namely structural characterisation of products resultant from Ge reaction with glycine (36) and amino acids quantification (37).