A novel capsule-like structure of micro-sized particles formed by phytosterol ester and γ-cyclodextrin in water

The composite material formed by phytosterol ester (PSE) and gamma-cyclodextrin (gamma-CD) disperses readily in water and has been used to mask undesirable flavours. This paper elucidates the structure of the PSE/gamma-CD particle. Cryogenic scanning electron microscopy and contact angle measurements showed that the PSE/gamma-CD particles formed a capsule-like structure with a hydrophilic surface. A phase-solubility study using cholesteryl oleate (ChO), one of the components of PSE, showed that ChO formed a hydrophilic and stoichiometric inclusion complex with gamma-CD at a molar ratio of 2: 5. The structure of the PSE/gamma-CD inclusion complex was similar to that of ChO/gamma-CD, based on differential scanning calorimetry and powder X-ray diffractometry results. Thus, we propose that the PSE/gamma-CD particle has a capsule-like structure wherein a hydrophobic PSE droplet is surrounded by an outer layer of the hydrophilic PSE/gamma-CD inclusion complex. (C) 2016 Elsevier Ltd. All rights reserved.