A review on cyclodextrin encapsulation of essential oils and volatiles

Cyclodextrins (CyDs) are cyclic carbohydrates derived from starch. The parent CyDs contain six, seven and eight glucopyranose units and are referred as alpha-, beta- and gamma-CyD, respectively. The most important property of the CyDs is the ability to establish specific interactions - molecular encapsulation - with various types of molecules through the formation of non-covalently bonded entities, either in the solid phase or in aqueous solution. These nano-encapsulating agents may form inclusion complexes with essential oils and volatiles, or their components, in order to improve their characteristics, such as transformation of liquid compounds into crystalline form; masking unpleasant smells and tastes of some compounds; improving the physical and/or chemical stability; and stabilizing volatile compounds by reducing or eliminating any losses through evaporation. Complexation has been used to avoid the destruction of certain flavours by processing or, on storage, allowing the use of minor amounts of flavours. The guest molecule is released in the warm moisture of the mouth. Examples are spices, essential oils of vegetable origin and plant flavours, chamomile oil and extract, eucalyptus oil, fennel oil, lemon oil, onion and garlic oil, camphor, menthol, thymol, etc. There are several methods for the preparation of inclusion complexes; kneading, co-precipitation, freeze-drying and spray-drying the most commonly used. Evidence for a guest inclusion into the apolar CyD cavity may be proved by various analytical techniques, including NMR spectroscopy, UV-visible absorption spectroscopy, optical rotatory dispersion and circular dichroism, fluorescence, infrared/FT-IR spectroscopy, thermo-analysis, TLC, mass spectromety, and powder X-ray diffractometry. Copyright (C) 2010 John Wiley & Sons, Ltd.