## 3 Results and Discussion
### Determination of Encapsulation Efficiency and Loading Capacity by UV Spectroscopy  
To determine the encapsulation efficiency, UV-visible spectroscopic measurements were undertaken. At first, the UV-VIS spectrum of the crude essential oil was recorded at appropriate dilution (Figure 3). The recorded spectrum shows a well-distinguished absorption maxima at 603 nm which can be attributed to the blue-colored chamazulene. Thus, further measurements were performed at this wavelength, and concentrations were determined using a calibration curve.  
The calibration diagram was constructed using the concentrations and measured absorbances of six different alcoholic solutions of AMO, ranging from 1 to 10 mg/mL. The resulting equation, y = 0.0492 X \(-\) 0.0033 with R\({}^{2}\) = 0.9993, demonstrates a high linear correlation between AMO concentrations and absorbances at 603 nm.  
The absorbances of the obtained freeze-dried microcapsules dissolved in ethanol were also measured. The AMO-containing microcapsules presented a maximum absorbance at 603 nm, whereas the microcapsules without oil (PL) showed no absorption maximum, indicating that the presence of oil can be detected in the microcapsule solutions.  
The encapsulation efficiency (EE) and loading capacity (LC) are presented in Table 6 and should be taken into consideration to determine the efficiency of the microencapsulation process [40; 43].  
The encapsulation efficiency refers to the amount of core material entrapped inside the microcapsules, serving as an important index for evaluating the efficiency of the microencapsulation [59; 60]. The EE value obtained in our experiment is relatively high and aligns well with the values reported in the literature obtained through complex coacervation. The ratio of encapsulation efficiency obtained by [PERSON] et al. ranged from 45.15% to 71.70% [58]. For the formulation tested by [PERSON] and [PERSON] with the method of complex coacervation, the values of EE varied from 89.7 to 98.7% [40]. The type and composition of the wall material, along with the drying process, play an important role in improving the EE values, which are typically high in complex coacervation involving gelatin in the shell [40; 59].  
Loading capacity refers to the amount of encapsulated core material relative to the total mass of the microcapsule. Various ranges of loading capacities have been reported in the literature, attributed to differences in the core material, macromolecule species, and the ratio of wall materials. [PERSON] et al. reported encapsulation loadings of nisin and avocado peel extract ranging from 3.05 to 13.59% and 4.58 to 20.54%, respectively [61], while the LC of coacervated black raspberry anthocyanin microcapsules prepared by [PERSON] et al. ranged from 29.67 to 38% [62].  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Yarrow Essential Oil** & **AMO Concentration** & **Concentration of** & **Oil Content** & **Total (Initial) Oil** & **EE\%** & **LC\%** \\
**in Microcapsules** & **mg/mL** & **mg/mL** & **mg/100 mg MC** & **mg/100 mg MC** & **mg/100 mg MC** & **25\%** & **LC\%** \\ \hline Total oil content & 5.961 & 15 & 39.74 & 40.29 & & & \\ Surface oil content & 0.667 & 15 & 4.45 & 40.29 & & 87.60 & 35.29 \\ \hline \hline \end{tabular}  
* Calculated based on the straight-line equation and the measured absorbance values.  
\end{table}
Table 6: Encapsulation efficiency and loading capacity for AMO microcapsules.