Evaluation of monoterpene-cyclodextrin complexes as bacterial growth effective hurdles

Monoterpenes have antimicrobial properties but are associated with strong smells and flavors that limit their use in foods; therefore, strategies to keep their effectivity using lower concentrations are required. This work tested the antimicrobial capacity of thymol, carvacrol and linalool free or complexed in hydroxypropyl-β-cyclodextrins (HP- β-CDs) using two complexation methods. To this, these monoterpenes were complexed in HP- β-CDs by the solubility method or a microwave-assisted method, spray dried and their antimicrobial capacity was tested on Escherichia coli and Staphylococcus aureus by determining minimal inhibitory concentration and minimal bactericidal concentration. The results show significant differences (p < 0.05) between the complexed and uncomplexed forms. In addition, thanks to the complexation of monoterpenes, the use of lower concentrations of these has been reached to achieve the same level of inhibition than uncomplexed forms. Likewise, it has been found that a lower minimal inhibitory concentration (MIC) is achieved for the solubility method for both microorganisms (3.82 mM for thymol and 2.44 mM for carvacrol in E. coli; and 3.91 and 2.61 mM, respectively for S. aureus) than for the microwave method. This implies that a lower concentration of these compounds can be used to inhibit microbial growth in foods, which should minimize their effects on their smell and taste.