## 3 Results and Discussion
### FT-IR Analysis of Microcapsules  
The FTIR spectrum of microencapsulated AMO and the comparison among wavenumbers of FTIR spectra related to the wall materials and unencapsulated core material are shown in Figure 8.  
The peaks observed in the FT-IR spectrum (Figure 8: AMO) of yarrow essential oil at 2958 cm\({}^{-1}\), 2926 cm\({}^{-1}\), and 2870 cm\({}^{-1}\) fall within the range of C-H stretching vibrations, typically associated with aliphatic hydrocarbons, indicating the presence of methylene (\(-\)CH\({}_{2}-\)) and methyl (\(-\)CH\({}_{3}\)) groups. The peaks at 1743 cm\({}^{-1}\), 1735 cm\({}^{-1}\), and 1712 cm\({}^{-1}\) correspond to carbonyl (C=O) stretching vibrations, characteristic of ester and ketone functional groups. Wavenumbers 1456 cm\({}^{-1}\) and 1448 cm\({}^{-1}\) correspond to C-H bending vibrations (scissoring) in alkanes, while 1381 cm\({}^{-1}\), 1367 cm\({}^{-1}\) and 1362 cm\({}^{-1}\) indicate C-H bending vibrations (wagging and twisting) in methyl (-CH\({}_{3}\)) groups. The peaks at 1022 cm\({}^{-1}\) and 1039 cm\({}^{-1}\) are due to C-O stretching vibration commonly found in alcohols, ethers, and esters. The peak at 875 cm\({}^{-1}\), located in the fingerprint region, could be associated with out-of-plane bending vibrations of C-H bonds, often seen in aromatic compounds or other complex structures [35; 63; 64]. These interpretations suggest that yarrow essential oil contains a variety of functional groups corresponding to the diversity of terpen and terpenoids, including saturated and unsaturated aliphatic hydrocarbons (alpha and beta-pinene, sabinene esters, cryophyllene, germacrene D, chamazulene, gamma-terpinene, D-limonene, etc. ), ketones (2-bornanone, piperitone, alpha thujone, artemisinin ketone, 4-acetyl-1-methylcyclohexene, etc. ), alcohols  
Figure 8: The FT-IR spectrum of yarrow essential oil (AMO), essential oil containing microcapsule (MC), unloaded microcapsule (PL), arabic gum (GA), and gelatin (GE). (linalool, endo borneol, terpinene 4-ol, etc. ), ethers (e.g., eucalypt, carophyllene oxide), esthers (e.g., bornyl acetate), and aromatic compounds (e.g., p-cymene, carvacrol, thymol). Arabic gum (GA, also known as gum acacia) is a complex mixture of polysaccharides and glycoproteins. The backbone of arabic gum is mainly composed of 1,3-linked \(\beta\)-D-galactopyranosyl units, with side chains of 1,3-linked \(\beta\)-D-galactopyranosyl units joined to it by 1,6-links. Both main chains and side chains have \(\alpha\)-L-arabinofuranosyl, \(\alpha\)-L-rhamopyranosyl, \(\beta\)-D-glucuronopyranosyl and 4-O-methyl-\(\beta\)-D-glucuronopyranosyl units attached. Arabic gum also contains a small proportion of protein (about 1-2%), which is covalently linked to the polysaccharide part. This component is important for the emulsifying properties of the gum [63]. The FT-IR spectrum of gum arabic (Figure 8: GA) is characterized by a strong absorption band at 3567 cm\({}^{-1}\), attributed to the -OH stretching vibration, indicative of free or hydrogen-bonded hydroxyl groups associated with the polysaccharide structure. The peak at 3212 cm\({}^{-1}\) corresponds to the stretching vibrations of N-H bonds, likely due to the protein component of arabic gum or amino acids present in its glycoprotein structure. A weaker peak at 2925 cm\({}^{-1}\), characteristic of C-H stretching vibrations in alkyl groups, suggests the presence of hydrocarbon chains within the polysaccharide structure. Additionally, peaks at 1617 cm\({}^{-1}\) and 1425 cm\({}^{-1}\) represent asymmetrical and symmetrical stretching vibrations of the carboxylate groups (-COO\({}^{-}\)), mainly attributed to glucuronic acid units. The strong absorption band at 1031 cm\({}^{-1}\) corresponds to the asymmetric stretching vibration of -C-O-C and -C-O, which are prevalent in polysaccharides, indicating glycosidic linkages and hydroxyl groups in arabic gum [35; 59; 64; 65; 66]. Gelatin is a polypeptide derived from collagen, primarily composed of the amino acids glycine, proline, hydroxyproline, and glutamic acid [39; 62].