Synthesis and characterization of β-cyclodextrin inclusion complexes of thymol and thyme oil for antimicrobial delivery applications

Microencapsulation with β-cyclodextrin (β-CD) as a delivery platform offers a promising application for natural antimicrobial delivery for food safety. Hence, this study aimed to characterize inclusion complexes of thymol and thyme essential oil with β-CD and their resulting antimicrobial activities. Inclusion complexes were prepared by kneading (KN) and freeze-drying (FD) methods. The entrapment efficiencies ranged from 71 to 83 g/100 g with higher (P < 0.05) values for thymol and FD particles. All particles showed irregular shapes and sharp edges with significant differences in size distribution and strong tendency to agglomerate. FD produced higher (P < 0.05) particle sizes than KN method. Differential Scanning Calorimetry (DSC) analysis confirmed inclusion complexes formation between β-CD and both compounds. Phase solubility tests indicated B_S-type complexes formation between thymol and β-CD. All compounds effectively inhibited bacterial growth within the concentration range tested. Free thyme oil showed higher (P < 0.05) antimicrobial activity than thymol, and FD β-CD inclusion complexes were able to inhibit Escherichia coli K12 at lower (P < 0.05) active compound concentrations than corresponding free oils. Antimicrobial activities of β-CD inclusion complexes against total viable counts in pork meat system throughout storage were observed. The FD method showed to be the best encapsulation method with enhanced antimicrobial activity for both compounds.