Preparation and characterization of tea oil powder with high water solubility using Pickering emulsion template and vacuum freeze-drying

In this study, tea oil powder was firstly prepared using Pickering emulsion template coupled vacuum freeze-drying with maltodextrin (MD) as wall material. The effect of MD content on the rheological properties of the Pickering emulsion was investigated. The solubility, moisture content, bulk density, encapsulation efficiency, and microstructure of the tea oil powder were evaluated when different concentration of xanthan gum/lysozyme nanoparticles (XG/Ly NPs) were used. The results showed that increasing NPs and MD substantially enhanced the viscoelasticity of Pickering emulsion. The prepared tea oil powder herein had a milky white appearance with water content less than 3.45% ± 0.09%. Its bulk density was 0.34 ± 0.06 g/cm3, and solubility could be as high as 87.13% ± 0.86%. The highest tea oil encapsulation rate reached 66.41% ± 0.01% when 50% MD and 4% XG/Ly NPs was used. The surface of tea oil powder showed a relatively smooth porous microstructure, while the addition of MD made its surface became irregular with porosity and puckering. Additionally, oxidation stability of tea oil powder could be regulated MD and NPs. The results demonstrated that tea oil powder with high water solubility and controlled oxidation stability could be prepared by Pickering emulsion template coupled with vacuum freeze-drying technology.