*3.2. Optimization of Microencapsulation of Leaf Essential Oil with β-Cyclodextrin*

The preparation method of microencapsulation can influence the property of βcyclodextrin microcapsules. Kfoury et al. (2016) studied the aroma release effect from the solid inclusion complexes of β-cyclodextrin with trans-anethole by two preparation methods, freeze-drying (FD) and co-precipitation coupled to FD (Cop-FD). Cop-FD microcapsules retained more efficiently trans-anethole than that of FD microcapsules; it revealed co-precipitation method provide superior inclusion characteristics [12].

The specimen to β-cyclodextrin ratio and the solvent ratio is the important factors that influence the yield of microcapsules. Yields of linalool and leaf essential oil microencapsulated with β-cyclodextrin by different reaction conditions are presented in Table 2. β-Cyclodextrin completely dissolved in the solution (ethanol/water, 1:2 *v/v*) by heating at 50 ◦C for 5 min, then the solution was cooled down to 25 ◦C without adding the core material, and no powders/crystals formed or precipitated even at 4 ◦C. The highest yield of microcapsule was 94.2% at the linalool to the β-cyclodextrin ratio of 15:85 (*w/w*), which was quite close to the molar ratio (linalool:β-cyclodextrin) of 1:1.


**Table 2.** Yields of linalool and leaf essential oil microencapsulated with β-cyclodextrin.

\*: Different letters (a–d and A–C) in Table refer to statistically significant difference at the level of *p* < 0.05 according to Scheffé's test.

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-cyclodextrin was 96.5%.
