Thermal, structural, antimicrobial, and physicochemical characterisation of thyme essential oil encapsulated in β- and γ-cyclodextrin

The present work aimed to encapsulate the thyme essential oil (TEO) in β-cyclodextrin (BCD) and γ-cyclodextrin (GCD) complexes in two selected cyclodextrin (CD) to TEO ratios (85/15 and 80/20 w/w) and compare the physicochemical, antioxidant, and antimicrobial properties of the encapsulated powders. The inclusion complexes between CD and TEO were prepared by blending aqueous CD and TEO in ethanol followed by freeze-drying. The powder properties were assessed by measuring particle size and microstructure using SEM, FTIR, and XRD. The median values of the particle sizes (GCD: 92.0 ± 4.69 and BCD: 46.2 ± 2.56-mm) significantly influenced the encapsulation efficiency, resulting in a higher encapsulation efficiency of the GCD (92.02 ± 10.79%) than that of the BCD (56.30 ± 12.19%). The encapsulated GCD/TEO (80/20) showed higher antioxidant activity and an antimicrobial inhibitory effect against Listeria monocytogenes and Salmonella enterica sv. typhimurium. Overall, the GCD acts as a superior wall material to the BCD in the TEO encapsulation.