Inulin potential for encapsulation and controlled delivery of Oregano essential oil

The ability of inulin, a prebiotic material, as encapsulation matrix was explored. Microcapsules of Raftiline were produced by spray drying inulin solutions at different solids content (5, 15 and 25%) at 120, 155 and 190 °C, according to a Central Composite Rotatable design. Produced capsules were analysed for morphology and size by SEM and physiochemical characterized by DSC, IR and RAMAN. Oregano essential oil was incorporated in the inulin solutions at 15% solids basis and the emulsions dried at the same conditions. The above mentioned methodologies were applied to evaluate the encapsulation ability and the changes induced by the presence of the EO in capsules morphology and structure. Furthermore the kinetics and amount of release was assessed by a spectrophotometric method. Results showed that it was possible to produce regular spherical inulin microcapsules (3–4.5 μm) for all the tested experimental conditions. According to IR and Raman results mainly drying temperature affected the structure of the capsules, three groups being clearly formed. These groups could be related to the morphology of inulin crystals. The EO was successfully encapsulated in the system as demonstrated by IR and Raman analysis. The differences found in the EO releasing amount, make clear that different degrees of core material retention is achieved, what should be related to structural changes in the matrix wall, denoting in some processing conditions interactions phenomena among inulin and EO. Those different releasing profiles patterns may be quite useful in finding different potential uses for the encapsulates.Thanks are due for the financial support given by Portuguese Foundation for Science and Technology (FCT) through the project PTDC/AGR/ALI/67194/2006 and through a post-doctoral grant of first author (SFRH/BPD/44200/2008) supported by programme QREN - POPH - Tipologia 4.1. The authors also express their gratitude to Mr Octavio Chaveiro from INIAV for the given support in microscopy studies