Submitted to: Controlled Release Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/12/2005
Publication Date: 4/1/2005
Citation: Liu, L.S., Chen, G., Fishman, M.L., Hicks, K.B. Pectin gel vehicles for citronellal delivery. Controlled Release Journal.2005. Drug Delivery. 12:p.149-157. Interpretive Summary: Although enormous quantities of pectin are avilable from U.S. fruit and sugar beet processing, only a limited amount is used in food industry. In order to add value to these underutilized agricultural residues, we explored new utilities of pectins for the non-food market. By using citronellal as a model volatile chemical, the study demonstrates that the release profile of incorporated volatiles can be specifically altered to the desired level for any applications by modifying the concentration and functional group of different types of pectin. It highlights the new use of pectin in the controlled release of cosmetics and household care products as well as for environmental protection. The pectin based gels provided superior release kinetics (sustained release over an longer period) compared to commercially used synthetic polymers such as polyvinyl pyrollidone (PVP).
Technical Abstract: In order to develop pectins as delivery carriers for the controlled release of volatile chemicals, two types of pectin formulations were prepared and studied: pectin gels from pectins with various degrees of esterification (D.E.) and calcium cross-linked pectin microparticles. Citronellal, a model nonpolar, volatile chemical, was incorporated into the pectin formulations. The release and partitioning of citronellal was evaluated with a kinetic method and by a static headspace method. The kinetic method indicates the rate at which volatiles are released to the vapor phase, whereas the static method determines the potential extent of volatiles released. This study showed that the pectin networks had major effects on the release of volatile chemicals. The increase in the D.E. of pectins induced a stronger molecular association with nonpolar volatiles, resulting in a prolonged duration of volatile release. The increase in pectin concentration in gel formulations increased the system viscosity, thus suppressing the volatile release by a diffusion mechanism. Therefore, by altering the structural and molecular characteristics of pectins the release of volatiles can be controlled and optimized for specific applications. Blocking the carboxyl groups of pectins with calcium ions reduces the hydrophilicity of pectins as indicated by measuring the contact angle of air bubbles between the pectin membrane and ethanol. Furthermore, the calcium chelation provides physical barriers for mass diffusion. The calcium initiated pectin microparticles are promising materials for the release of volatiles for a prolonged duration.