Encapsulation of Natural Flavors in Cyclodextrins: Free Volume Studies by PALS

Positron annihilation lifetime spectroscopy (PALS) is used to study the free-volume in beta-cyclodextrin (CD) with the encapsulation of two different essential oils: garlic (Allium sativum) and marjoram (Origanum majorana). The data reveal the presence of a long lifetime component related to the o-Ps. It is observed that the addition of garlic (or marjoram) oil to beta-CD results in a decrease of the o-Ps lifetime which was ascribed to a reduction of the free volume holes from 83.6 to 67.7 angstrom(3) (79.1 to 72.6 angstrom(3)). Different mechanisms for the encapsulation of garlic and marjoram oils in beta-CD are suggested by the PALS parameters.