Physical Properties and Stabilization of Microcapsules Containing Thyme Oil by Complex Coacervation

The aim of this study was to produce and characterize microcapsules of thyme oil and finally appraise the extent of stability improvement. The optimum process conditions obtained from orthogonal tests were as follows: ratio of core material to wall 0.5, temperature 40 °C, pH value 3.0 and time 20 min, where the practical encapsulation efficiency was 85.17±1.35%. The microcapsules belong to the nanometric range as the average particle diameter was 531.17±77.12 nm. The results from structural analysis indicated that no significant chemical bond occurred during the encapsulation process and the microcapsules remained stable when the encapsulation was conducted at a temperature below 53.1 °C. Especially, the retention rate of thyme oil in microcapsules remained 39.21% at 4 °C, 36.99% at 25 °C and 33.80% at 40 °C after 30 d of storage. Moreover, protection from light exposure presented a positive impact on the storage stability of thyme oil microcapsules.