Release characteristics of antibacterial substances included in cyclodextrin

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Encapsulation of hydrophobic plant essential oil (liquid antibacterial substances or food flavor) in cyclodextrin (CD) is an attractive method for improving the stability of these compounds during manufacture and storage. Furthermore, it is often required that the substances included should be controllably released during consumption. This study investigated mainly the mechanism of release of allyl isothiocyanate (AITC) included in b-cyclodextrins during storage under various temperatures and humidities. Further, a novel technique of measuring release rate was developed, in which the release characteristics was investigated under a elevated temperature condition. The results are as follows :1) The inclusion complex CD powders of AITC was effectively prepared with a twin-screw kneader. The molar ratio of AITC to b-CD was dependent on the kneadingtorque.2) The release rate to AITC was depend not only on tempetature but also on relative humidity (RH). The release of AITC could be approximated as a first order reaction equation of the remaining amount of AITC in the first stage. The kinetic energy of release, calculated on the basis of the first order reaction approximation, was markedly decreased with an increase in RH.This indicates that the release of AITC from the complexing powder was caused by the adsorption of the water on cyclodextrin molecules. The release rate of AITC was well correlated with the concentration of water vapor in the air stream.3) The temperature-programd release method was used as a simplfied method for measuring release rate of guest substances from the complex powder. The temperature of the sample powder at the maxium concentration of the guest substance in the carrier nitrogen gas was related to the activation energy of release and the frequency factor. The mathematical model was established to calculate these reaction parameters.