*3.3. Stabilization and Release of Leaf Essential Oil Microcapsules*

The constituents of common essential oils from aroma plants are small molecular weight and highly volatile. The encapsulation of limonene would influence its properties, such as evaporation, stabilization and controlled release, by different encapsulation methods and selected materials. The retention of limonene in extruded starch (nonencapsulation) was quite low (8.0%) compared with that of limonene microencapsulated with β-cyclodextrin (92.2%) [20].

Using the accelerated dry-heat aging test to evaluate the stability and release of leaf essential oil microcapsules. Figure 3 shows the weight losses of β-cyclodextrin (β-CD), linalool-chemotype leaf essential oil (LL oil), and leaf oil microcapsules (β-CD/LL oil) at 105 ◦C during the accelerated aging period. The weight loss of β-CD was very slight (less than 0.5%) after 8 days of the accelerated aging test; it indicated that β-CD was thermostable at 105 ◦C. Trotta et al. (2000) investigated the thermal behavior of β-CD; the decomposition temperature of β-cyclodextrin was 250 ◦C by using the thermogravimetric analysis (TGA) [39]. Weight losses of linalool-chemotype leaf essential oil was 99.1% after

30 min at 105 ◦C (data not shown in Figure 2); leaf essential oil exhibited highly volatile in the high-temperature environment. Weight losses of leaf essential oil microcapsules were 6.73%, 9.33%, 12.14%, and 13.40% after 1, 2, 4, and 8 days of the aging test, respectively. Results revealed that microencapsulation with β-cyclodextrin slowed down the release/emission of leaf essential oil in the dry-heat aging test and improved the thermal stabilization of linalool-chemotype leaf essential oil. min at 105 °C (data not shown in Figure 2); leaf essential oil exhibited highly volatile in the high-temperature environment. Weight losses of leaf essential oil microcapsules were 6.73%, 9.33%, 12.14%, and 13.40% after 1, 2, 4, and 8 days of the aging test, respectively. Results revealed that microencapsulation with β-cyclodextrin slowed down the release/emission of leaf essential oil in the dry-heat aging test and improved the thermal stabilization of linalool-chemotype leaf essential oil.

As for the ethanol/water ratio, the highest yield of microcapsule was 98.1% under the 1:5 ratio of ethanol to water. There was no statistically significant difference in the microcapsule yields between the solvent ratio of 1:3 and 1:5 (*p* < 0.05). Using the optimal reaction conditions, the yield of linalool-chemotype leaf essential oil microencapsulated with β-

The constituents of common essential oils from aroma plants are small molecular weight and highly volatile. The encapsulation of limonene would influence its properties, such as evaporation, stabilization and controlled release, by different encapsulation methods and selected materials. The retention of limonene in extruded starch (non-encapsulation) was quite low (8.0%) compared with that of limonene microencapsulated with β-

Using the accelerated dry-heat aging test to evaluate the stability and release of leaf essential oil microcapsules. Figure 3 shows the weight losses of β-cyclodextrin (β-CD), linalool-chemotype leaf essential oil (LL oil), and leaf oil microcapsules (β-CD/LL oil) at 105 °C during the accelerated aging period. The weight loss of β-CD was very slight (less than 0.5%) after 8 days of the accelerated aging test; it indicated that β-CD was thermostable at 105 °C. Trotta et al. (2000) investigated the thermal behavior of β-CD; the decomposition temperature of β-cyclodextrin was 250 °C by using the thermogravimetric analysis (TGA) [39]. Weight losses of linalool-chemotype leaf essential oil was 99.1% after 30

*Molecules* **2021**, *26*, x FOR PEER REVIEW 6 of 8

*3.3. Stabilization and Release of Leaf Essential Oil Microcapsules* 

cyclodextrin was 96.5%.

cyclodextrin (92.2%) [20].

**Figure 3.** Changes in weight loss of leaf essential oil microcapsules during the dry-heat aging period. β-CD: β-cyclodextrin; LL oil: *C. osmophloeum* leaf oil; β-CD/LL oil: leaf oil microcapsules; different letters (a–e) in the figure refer to the statistically significant difference at the level of *p* < 0.05 according to the Scheffé's test. **Figure 3.** Changes in weight loss of leaf essential oil microcapsules during the dry-heat aging period. β-CD: β-cyclodextrin; LL oil: *C. osmophloeum* leaf oil; β-CD/LL oil: leaf oil microcapsules; different letters (a–e) in the figure refer to the statistically significant difference at the level of *p* < 0.05 according to the Scheffé's test.
