# Encapsulation of Fennel Essential Oil in Calcium Alginate Microbeads via Electrostatic Extrusion
## 3 Results and Discussion
### Characterization of the Essential Oil by GC-MS
Figure 3: GC-MS chromatogram of the fennel EO prior to encapsulation (1 = \(\alpha\)-Pinene; 2 = Camphene; 3 = Sabinene; 4 = \(\beta\)-Pinene; 5 = Myrcene; 6 = \(\alpha\)-Phellandrene; 7 = \(\alpha\)-Terpinene; 8 = \(p\)-Cymene; 9 = D-Limonene; 10 = Eucalypt; 11 = \(\gamma\)-Terpinene; 12 = _cis_-Sabinene hydrate; 13 = L-Fenchone; 14 = Camphor; 15 = Estragole; 16 = Nerol (internal standard); 17 = Carvone; 18 = \(p\)-Anisaldehyde; 19 = trans-Anethole). Trans-anethole was the main representative of phenylpropanoids and the most abundant compound in both oils, which is consistent with previous data [1; 40; 41]. L-fenchone was the dominant representative of oxygenated monoterpenoids, while \(\alpha\)-pinene, D-limonene, and myrcene were the most abundant monoterpene hydrocarbons. The content of \(p\)-anisaldehyde was also relatively high compared to other constituents. [PERSON] et al. [42] and [PERSON] et al. [1] observed a similar composition of the fennel EO prior to and after encapsulation by spray-drying and during hydrodistillation and steam distillation of fennel EO from seeds with or without pretreatment by cryogrinding, respectively. As for the quantitative aspect, the results highlighted notable variances in the levels of compounds between the original and encapsulated EO. It was observed that the concentrations of all compounds were reduced in the encapsulated EO compared to the original EO, except for carvone, where no significant differences were observed in its concentration between the two oils. The most significant reduction (63.8%) was observed for monoterpene hydrocarbons, followed by aromatic aldehydes (46.4%) and oxygenated monoterpenes (18.7%), while the relative amount of phenylpropanoids rose 17.6% on account of other groups. The retention of EO constituents within a polymer matrix largely depends on their volatility and hydrophobicity, which was demonstrated as highly relevant in the case of monoterpene hydrocarbons whose hydrophobic nature increased their concentration on the particle surface, leaving them less protected and more prone to volatilization [43]. The process of freeze-drying, which proved to be superior in terms of volatiles' retention over other drying techniques [44; 45], also plays a significant role in EO retention. During the initial phase of freeze-drying, volatile substances possess vapor pressures higher than ice at the freezing temperatures, resulting in their swift evaporation from both the surface and interior of the frozen microbead, and compounds with higher volatility usually exhibit lower retention [46], which was observed in the present study. In addition, as the frozen water within the microbeads sublimates, it creates pores and voids within the alginate-whey protein structure of the beads, enabling, therefore, pathways for moisture vapor and volatile compounds to escape from the beads. During the advanced freeze-drying phase, the retention of compounds is improved by sorption or locking due to the partially dried hydrogel matrix [46]. Despite noting a substantial loss of compounds during the encapsulation process employing electrostatic extrusion followed by freeze-drying, the mean retention rate reached 58.95%, signifying the effective preservation of a large portion of fennel EO encapsulated with 1.5% alginate and 0.75% whey protein, thus paving the way for future research of this encapsulation technique.