Release characteristics of antibacterial substances included in cyclodextrin

疏水植物精油（液体抗菌物质或食品香精）在环糊精（CD）中包封是提高这些化合物在生产和储存过程中的稳定性的一种有吸引力的方法。此外，通常要求所含物质应在消费过程中可控地释放。本文主要研究了b-环糊精在不同温度和湿度下贮存过程中异硫氰酸烯丙酯（AITC）的释放机理。此外，还开发了一种新的释放速率测量技术，研究了在高温条件下的释放特性。结果表明：1)采用双螺杆捏合机可有效制备AITC包合CD粉体。AITC与b-CD的摩尔比与捏合力矩有关。2)对AITC的释放速率不仅与温度有关，还与相对湿度（RH）有关。AITC的释放可以近似为AITC在第一阶段剩余量的一级反应方程。根据一级反应近似计算的释放动能随相对湿度的增加而显著降低。说明环糊精分子吸附了水，从而使AITC从络合粉中释放出来。AITC的释放速率与气流中水蒸气浓度有良好的相关性。3)采用程序升温释放法作为测量复合粉体客体物质释放速度的简化方法。样品粉末在载氮中客体物质最大浓度时的温度与释放活化能和频率因子有关。建立了数学模型来计算这些反应参数。

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.