Formation of essential oil containing microparticles comprising a hydrogenated vegetable oil matrix and characterisation thereof.

Microparticles with different essential oil concentrations 0, 75, 150, 225 and 300 gkg-1, (g of essential oil per kg of microparticles), were produced by dispersing the essential oils within a hydrogenated vegetable fat matrix and forming spherical solid particles by spray-chilling. Size distribution, flowability, surface structure, essential oil recovery, melting properties and crystallinity of the microparticles were determined. With over 225 gkg-1 essential oil the microparticle surface became stickier, their flowability was reduced and the size distribution broadened. Gas chromatography showed that the essential oil recovery was always above 85% v/v. The surface structure of the microparticles was strongly affected by the essential oil concentration being smooth (225 gkg-1), comprising round-shaped dumps (300 gkg-1) or showing fat blooming (0, 75, 150 gkg-1). With essential oil, the formation of the β-polymorphic form of the triglycerides was supported leading to changes in the melting behaviour and the crystalline structure.