Encapsulation of lemongrass oil with cyclodextrins by spray drying and its controlled release characteristics

Inclusion of the two isomers of citral (E-citral and Z-citral), components of lemongrass oil, was investigated within the confines of various cyclodextrin (-CD, -CD and -CD) host molecules. Aqueous complex formation constants for E-citral with -CD, -CD and -CD were determined to be 123, 185, and 204 L/mol, respectively, whereas Z-citral exhibited stronger affinities (157, 206, and 253 L/mol, respectively). The binding trend -CD>-CD>-CD is a reflection of the more favorable geometrical accommodation of the citral isomers with increasing cavity size. Encapsulation of lemongrass oil within CDs was undertaken through shaking citral:CD (1:1, 1.5:1, and 2:1 molar ratio) mixtures followed by spray drying. Maximum citral retention occurred at a 1:1 molar ratio with -CD and -CD demonstrating the highest levels of total E-citral and Z-citral retention, respectively. Furthermore, the -CD complex demonstrated the slowest release rate of all inclusion complex powders.