Characterization of core–shell structures formed by zein

Core–shell structures are of interest for encapsulation purposes in the food, pharmaceutical, and cosmetics industries. A number of wall materials are in use including carbohydrates, lipids, and proteins. Zein, the prolamin of corn, is capable of self-assembly into microspheres, potentially useful in encapsulation and delivery systems. In previous work, zein was observed to form core–shell structures with citral and lime by evaporation induced self-assembly of zein in ethanol–water. The objectives of this work were to investigate the effect of mass ratio of core to shell materials and ethanol content of the solvent on encapsulation microstructure. Scanning electron microscopy (SEM), focused ion beam (FIB), and transmission electron microscopy (TEM) were used for structure characterization. Raman spectroscopy and FTIR were used to detect citral or lime in the core. Microstructure images suggested that core–shell structures of zein loaded with lime flavor were formed only in a narrow range of core to shell mass ratio. Ethanol content also affected structure formation.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Zein self-assembled into microspheres, potentially useful in encapsulation. ► Core–shell structures of citral and zein were observed by SEM and TEM. ► Core–shell was only observed within a narrow range of core to shell mass ratio. ► Binary (ethanol–water) solvent composition affected core–shell formation. ► The presence of citral in the core was detected by Raman spectroscopy.