## 3 Results and Discussion
### Aldehydes
Some enzymes such as alcohol dehydrogenase and cis/trans isomerase convert these compounds into their corresponding alcohols and cis/trans isomers, respectively [30]. (Z,Z)-3.6-nonadienal is often cited in the literature, but is not easily identified because it rapidly isomerizes to 2,6-nonadienal and 2-nonenal [31, 34, 36]. Some authors have defined it \"watermelon aldehyde\" [30], since it has a low odor threshold and a strong aroma of \"freshly-cut watermelon\". Despite its instability, (Z,Z)-3,6-nonadienal was detected in \begin{table}
\begin{tabular}{c c c c c c c} \hline  & & & **WDF\_t0** & **WDF\_t1** & **WDF\_t2** & \\ \hline
**Analyte** & **Aroma** & **LRI** & **Area (\(\times 10^{6}\))** & **Area (\(\times 10^{6}\))** & **Area (\(\times 10^{6}\))** & **Ref** \\ \hline (E)-2-Pentenal &
\begin{tabular}{c} Pungent, green, fruity, apple \\ \end{tabular} & 758 & \(33.6\pm 0.3\) & 9.52  & - & [23, 27, 29, 32] \\ \hline
3-Methyl-2-butenal &
\begin{tabular}{c} Sweet, fruity, pungent, nutty \\ \end{tabular} & 784 & \(9.29\pm 0.06\) & \(12.6\pm 0.1\) & - & - \\ \hline Hexanal & Green, fatty, fruity, woody & 798 & \(119\pm 0.5\) & 196 & \(298\pm 0.6\) & [2, 23, 27, 29] \\ \hline
2-Ethyl-3-methylbutanal & - & 833 & - & - & 8.17  & - \\ \hline (Z)-2-Hewenal & Green & 837 & \(1.06\)  & - & - & [6] \\ \hline (E)-2-Hexenal & Green leaf, almond, fruity & 843 & \(42.2\pm 0.2\) & \(14.1\pm 0.1\) & - & [6, 23, 31, 32] \\ \hline
4-Heptnal & - & 878 & \(3.25\pm 0.55\) & 2.43  & - & [2, 23, 27, 29] \\ \hline Heptnal & Fresh, fatty, green, grass & 880 & \(11.9\pm 0.1\) & \(12.6\pm 0.2\) & \(13.9\pm 0.07\) & [6, 10, 23, 27] \\ \hline (E,E)-2-4-Hexacional & Green, fruity, citrus, waxy & 890 & \(3.36\)  & 5.41 \(\pm\) 0.06 & - & [10, 23] \\ \hline (E)-2-Heptnal & Green, fatty, oily, fruity & 923 & \(18.7\pm 0.2\) & \(29.0\pm 0.4\) & - & [23, 29, 31, 32] \\ \hline Octanal & Orange, waxy, green peel & 954 & \(7.35\)  & \(22.0\pm 0.3\) & \(13.3\pm 0.1\) & [10, 23, 31, 32] \\ \hline (E,E)-2,4-Heptadienal & Fatty, sweet, melon, spicy & 963 & \(10.9\pm 0.3\) & \(8.04\pm 0.08\) & - & [10, 23, 31, 32] \\ \hline Benzenecaetaldehyde & Honey, sweet, rose, floral & 994 & \(64.7\pm 0.5\) & 41.1 \(\pm\) 0.4 & - & [26, 29] \\ \hline (E)-4-Nonenal & Fruity & 1017 & \(18.1\pm 0.4\) & - & - & [6, 10, 23, 29] \\ \hline Nonanal & Waxy, citrus, cucumber & 1023 & \(74.2\pm 0.5\) & \(70.9\pm 0.6\) & \(12.9\pm 0.2\) & [2, 6, 23, 33] \\ \hline (Z,Z)-3,6-Nonadienal & Fresh-cut watermelon & 1046 & \(7.88\pm 0.06\) & - & - & [26, 30, 32, 34] \\ \hline (Z)-2-Nonenal & Cucumber, fatty, waxy & 1052 & \(6.91\pm 0.06\) & - & - & [2, 6, 30, 34] \\ \hline (E,E)-2,6-Nonadienal & Melon, cucumber, fatty & 1054 & \(4.47\)  & - & - & [6, 10, 27] \\ \hline (E,Z)-2,6-Nonadienal & Cucumber, melon, green & 1059 & \(237\pm 0.5\) & 21.7 \(\pm\) 0.3 & - & [2, 23, 29, 32] \\ \hline (E)-2-Nonenal & Fatty, green, melon & 1062 & \(266\pm 0.6\) & 23.4 \(\pm\) 0.2 & - & [2, 28, 29, 32] \\ \hline Decanal & Zest, waxy, orange, floral & 1090 & \(19.7\pm 0.2\) & \(11.7\pm 0.2\) & - & [6, 10, 23] \\ \hline (E,E)-2,4-Nonadienal & Cucumber, melon, waxy & 1101 & \(6.56\pm 0.1\) & \(6.64\pm 0.07\) & - & [6, 10, 23, 30] \\ \hline (E)-2-Decanal & Waxy, fatty, earthy & 1128 & \(8.67\)  & 15.0 \(\pm\) 0.1 & - & [6, 10, 29, 33] \\ \hline (E,Z)-2,4-Decanal & Fatty, orange, citrus, fresh & 1165 & \(4.66\)  & - & - & [6, 23, 26, 32] \\ \hline Dodecanal & Soapy, waxy, citrus, floral & 1214 & \(2.36\pm 0.06\) & - & - & [6] \\ \hline \end{tabular}
\end{table} 
Table 1: \(Cont.\)WDF_t0. It is likely that the fresh fruit of this cultivar had a particularly strong aroma that persisted in WDF_t0. 2,6-nonadienal and 2-nonenal are also particularly unstable. They have a \"green\" and \"waxy\" aroma and are characteristic of cucumber flavor. A progressive decrease in their abundance occurred over time until complete disappearance after 24 months.