Microencapsulation of Thymus fontanesii extracts in pectin/casein: characterization, release behavior and storage stability

The present study aims to enhance the stability of Thymus fontanesii essential oil (TEO) and its main component thymol, and to prolong their release from encapsulation in pectin/casein matrix using complex coacervation and dried by freeze methods. Encapsulation efficiency, structural, physical and thermal properties of the microcapsules were determined. Storage stability of free and microencapsulated thyme extracts was evaluated and the controlled release kinetics of microcapsules in simulated gastrointestinal fluids were studied. Respectively, the successes of TEO and thymol encapsulation were confirmed by FTIR and X-ray diffraction analyses with encapsulation efficiency of 91.85 ± 1.35% and 93.66 ± 1.13%. The particle size ranged from 4.47 to 517.20 μm, presented a good thermal resistance and irregular shapes with rough surface. Prolonged release of the extracts from microcapsules was demonstrated with Higuchi behavior in gastric fluids while for simulated intestinal fluid, the non-Fickian transport was the main release mechanism. The microencapsulation of thyme extracts enhanced its thermal stability and proved that the thyme extracts were effectively well protected in microcapsules after a long time storage. The use of pectin/casein has shown good performance as a biodegradable matrix for protection and storage of thyme extracts, prolonging their storage stability and release. Therefore, these microcapsules can be useful ingredients for both food and pharmaceutical new products, to prolong bioavailability of bioactive compounds and to improve their thermal and storage stability.