## 3 Results and Discussion
### ATR-FTIR Spectra Interpretation of the Outer Surfaces of Cucumber Peels  
The ATR-FTIR spectra bands observed on the outer surfaces of cucumber peels during the storage period (as depicted in Table 2 and Figure 4) were within the spectral range of 4000-499 cm\({}^{-1}\). The analysis of these spectra led to several significant findings. The bands located at 3334-3338 and 1635-1641 cm\({}^{-1}\), which are, respectively, associated with the stretching and bending vibrations of hydroxyl groups present in water, carbohydrates, organic acids, and phenols [12; 25], exhibited consistent high intensities throughout the storage period, indicating stability across all cucumber samples. Conversely, the bands at 2922 and 2854 cm\({}^{-1}\), linked, respectively, to asymmetrical and symmetrical C(sp\({}^{3}\))-H stretching vibrations of methylene groups found in terpenoids, carboxylic and fatty acids, saponins, carbohydrates, and free amino acids [12; 24], displayed a notable (\(p<0.05\)) and progressive increase from day 1 to day 16. Subsequently, the absorbance at 2922 cm\({}^{-1}\) reached a plateau, while the absorbance at 2854 cm\({}^{-1}\) showed a significant (\(p<0.05\)) decrease until day 22, followed by a slight insignificant increase toward the end of the storage period. Figure 3: Variation in image analysis computed features [mean, standard deviation, dissimilarity, short-run emphasis (SRE), run length non-uniformity (RLN), gray-level non-uniformity (GLN), and long-run emphasis (LRE)] of cucumber peel samples at days 1, 7, 13, 16, 22, and 28. Notably, the appearance of the band at 1460 cm\({}^{-1}\), attributed to the bending vibrations of methylene groups ([PERSON] et al., 2016), was observed for the first time on day 16 and maintained a constant intensity until the end of the storage period, likely associated with the increased intensities of C(sp\({}^{3}\))-H stretching vibrations. The band at 1724-1726 cm\({}^{-1}\), which is related to the stretching vibrations of the carbonyl group (C=O) in carboxylic acids ([PERSON] et al., 2016), exhibited a significant (\(p<0.05\)) increase at day 13 and subsequently showed no significant variation until the end of the storage period. The observed fluctuations in the C(sp\({}^{3}\))-H and C=O vibrations may be linked to a gradual increase in the organic acid content within the cucumber peel throughout the storage period. This hypothesis is supported by the findings of [PERSON] et al. (2017), who suggested that the storage of fruits at room temperature could result in an increase in organic acid concentration. According to [PERSON] et al. (2013), cucumber peel contains a high concentration of lactic acid, which has been demonstrated to prevent the growth of harmful germs to improve human health by boosting the immune system ([PERSON] et al., 2017). Furthermore, the band at 1546-1552 cm\({}^{-1}\), which is associated with the aromatic ring  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Regions (cm\({}^{-1}\))** & **Day 1** & **Day 7** & **Day 13** & **Day 16** & **Day 22** & **Day 28** \\ \hline
3334–3338 & 0.869 \(\pm\) 0.022 a & 0.859 \(\pm\) 0.033 a & 0.870 \(\pm\) 0.043 a & 0.853 \(\pm\) 0.075 a & 0.863 \(\pm\) 0.032 a & 0.890 \(\  
stretch [26], presented a significant (_p_ < 0.05) decrease on day 13 and subsequently remained constant until the end of the storage period. The bands at 1415-1420 and 1317-1319 cm\({}^{-1}\), which are ascribed to the combination of C-H rocking and O-H bending vibrations and to O-H in-plane bending vibrations [11; 24], respectively, in organic acids and primary or secondary alcohols, showed a significant (_p_ < 0.05) increase from day 1 to day 16, followed by a decrease at day 22. Similar alterations were presented for the intensities of the bands at 1234-1245, 1149-1155, 1097-1101, and 1022-1028 cm\({}^{-1}\), which are due to the C-O stretching vibrations of carbohydrates, polysaccharides, and phenolics [12; 29].