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Characterization of ß-cyclodextrin inclusion complexes of thymol and thyme oil for antimicrobial delivery applications

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  131590805,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: http://dx.doi.org/10.13031/aim.20131590805) @2013
Authors:   Feifei Tao, Laura E. Hill, Yankun Peng, Carmen L. Gomes
Keywords:   natural antimicrobials, ß-cyclodextrin, delivery systems, food safety, essential oils

Abstract. Microencapsulation with β-cyclodextrin (β-CD) as a delivery platform offers very promising applications in natural antimicrobial delivery for food safety protection. The objective of this study was to characterize inclusion complexes of thymol and thyme oil with β-CD and their resulting antimicrobial activity against foodborne pathogens. The inclusion complexes were prepared by kneading (KN) and freeze drying methods (FD). The entrapment efficiencies (EE) ranged from 72 to 83%, where thymol was more efficiently entrapped (P<0.05) than thyme oil, with FD method showing a higher (P<0.05) EE. All particles showed irregular shapes and smooth surfaces with significant differences in size distribution and strong tendency to agglomerate. FD had higher (P<0.05) particle sizes than KN method. DSC analysis confirmed the formation of inclusion complexes between β-CD and compounds. The phase solubility tests indicated the formation of BS-type complexes between β-CD and thymol. Thymol and thyme oil and their inclusion complexes were analyzed for their antimicrobial activity against Escherichia coli K12 (E. coli K12) using a microbroth dilution assay. All compounds effectively inhibited bacterial growth within the concentration range tested. The β-CD inclusion complexes formed by FD method were able to inhibit E. coli K12 at lower (P<0.05) active compound concentrations than corresponding free oils. Free thyme oil showed higher (P<0.05) antimicrobial activity than thymol, likely due to synergistic activity occurring among the compounds present in the oil that would increase their antimicrobial potency. The FD method showed to be the best encapsulation method with enhanced antimicrobial activity for both compounds.

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