## 3 Results and Discussion
### Ft-Ir  
Fourier transform infrared spectroscopy (FTIR) is an analytical technique for identifying and verifying chemical compounds. This method allows for the determination of molecular composition and the elucidation of molecular structure. Compounds exhibit selective absorption of infrared radiation based on their characteristic functional groups. When these compounds absorb energy, their molecules undergo stretching and bending vibrations influenced by their geometric configurations. The spectrum can be expressed as a function of wave number within the range of 14,000 cm\({}^{-1}\) to 25 cm\({}^{-1}\). However, the spectrum most commonly employed in sample analysis is the mid-infrared spectrum, i.e., within the wave number range from 4000 cm\({}^{-1}\) to 400 cm\({}^{-1}\). Occasionally, the spectrum is also represented in terms of transmission as a function of wave number. The absorption spectrum functions as a molecular identifier, with its distinctive pattern enabling qualitative and quantitative analyses. According to [PERSON]'s law, the intensity of the bands within the IR spectrum is proportional to the concentration of the compounds [58; 59; 60]. The spectral analysis revealed absorption bands corresponding to the vibrations of functional groups from the main components of peppers, including carotenoids, phenolic compounds, and ascorbic acid [61]. The 3000-3600 cm\({}^{-1}\) band was attributed to hydroxyl group (-OH) stretching vibrations from water and phenolic compounds. In the 3000-2800 cm\({}^{-1}\) range, two peaks indicated alkyl group (-CH\({}_{2}\) and -CH\({}_{3}\)) stretching vibrations. The 1730-1650 cm\({}^{-1}\) bands confirmed the presence of aldehydes, ketones, and carboxylic acids through carbonyl group (C=O) vibrations. Adjacent bands at 1617-1580 cm\({}^{-1}\) and 960 cm\({}^{-1}\) represented C=C bond vibrations from carotenoids. Bands at 1460-1430 cm\({}^{-1}\) and 1400-1360 cm\({}^{-1}\) were linked to methylene (-CH\({}_{2}\)) and methyl (-CH\({}_{3}\)) group vibrations, while those at 1270-1220 cm\({}^{-1}\) and 1160-1120 cm\({}^{-1}\) corresponded to (-C-O-C), (-C-O), and (C-N) group vibrations, indicating saccharides and other compounds. Bands at 1050-990 cm\({}^{-1}\) suggested the presence of (-C-O) and (-C-C) bonds, and those at 860-730 cm\({}^{-1}\) were attributed to aromatic (C-H) and C-Cl bonds [24; 31; 58; 60; 61]. Sonication altered the intensity of functional group bands, affecting antioxidant properties (Figure 4). Samples subjected to brief sonication (S_1, S_3) had reduced (-OH) group intensities but increased alkyl group (-CH\({}_{2}\) and -CH\({}_{3}\)) intensities, impacting aroma and flavor. Immersion ultrasound treatments (US_15, US_30) showed opposite trends. Similarpatterns were observed for (C=O), (-C-O-C), (C--N), and (-C-O) groups. The (C=C) group showed consistent intensities, except in US_15, where they decreased. The highest and lowest intensities for (-C-C) and aromatic (CH) groups were seen in US_30 and US_15, respectively. These results indicate pre-treatment parameters influenced the chemical composition and properties of peppers. Fermented pepper samples also exhibited variability in functional group intensities (Figure 4). The (-OH) group was most intense in fermented samples with prior sonication (S_5_F) and the fermented control, while it was weakest in samples with brief contact sonication (S_3_F, T_1_F). Conversely, alkyl groups (-CH2, -CH3) and others (C=O, C=C, (--C-O-C), (C-N)) were most intense in S_3_F and T_1_F. The (-C-C) and aromatic (CH) groups showed consistent intensities except in S_3_F and S_1_F, where they were lower. Fermentation and sonication influenced the chemical composition, particularly in contact sonication for 1-3 min. Comparable FTIR results were reported for _Capsicum annum_ L. var. serrano [61]. [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] [31] highlighted ultrasound effects on dried red pepper composition, showing reduced functional group intensities post-treatment.