Polylactide-Based Thyme Oil Microcapsules Production: Evaluation of Surfactants

The objective of this work is to prepare microcapsules of polylactide-containing thyme oil by coacervation using a variety of nonionic surfactants with different hydrophilic-lipophilic balance (HLB) values and evaluate the encapsulation efficiency of polar and apolar compounds of oil. Thus, Tween 20, Tween 80, Tergitol 15-S-9, and a combination of Tergitol 15-S-9 with Span 85 have been used. The HLB value was comprised between 11 and 16.5. For all the studied cases, microcapsules are spherical in shape and have bimodal particle size distribution with mean size between 30 and 40 mu m. The amount of encapsulated thyme oil reaches a maximum of 65% for Tergitol 15-S-9, a polyglycol ether surfactant with a HLB value of 13.3. The results confirm the dependence of the encapsulation efficiency as result of the hydrophobic properties of the surfactants. Moreover, it was confirmed a preferential encapsulation of apolar compounds of thyme oil in detriment of polar ones.