Synergies of carvacrol and 1,8-cineole to inhibit bacteria associated with minimally processed vegetables

This study assessed the occurrence of an enhancing inhibitory effect of the combined application of carvacrol and 1,8-cineole against bacteria associated with minimally processed vegetables using the determination of Fractional Inhibitory Concentration (FIC) index, time-kill assay in vegetable broth and application in vegetable matrices. Their effects, individually and in combination, on the sensory characteristics of the vegetables were also determined. Carvacrol and 1,8-cineole displayed Minimum Inhibitory Concentration (MIC) in a range of 0.6-2.5 and 5-20 mu L/mL, respectively, against the organisms studied. FIC indices of the combined application of the compounds were 0.25 against Listeria monocytogenes, Aeromonas hydrophila and Pseudomonas fluorescens, suggesting a synergic interaction. Application of carvacrol and 1,8-cineole alone (MIC) or in a mixture (1/8 MIC + 1/8 MIC or 1/4 MIC + 1/4 MIC) in vegetable broth caused a significant decrease (p<0.05) in bacterial count over 24 h. Mixtures of carvacrol and 1,8-cineole reduced (p<0.05) the inocula of all bacteria in vegetable broth and in experimentally inoculated fresh-cut vegetables. A similar efficacy was observed in the reduction of naturally occurring microorganisms in vegetables. Sensory evaluation revealed that the scores of the most-evaluated attributes fell between like slightly and neither like nor dislike. The combination of carvacrol and 1,8-cineole at sub-inhibitory concentrations could constitute an interesting approach to sanitizing minimally processed vegetables. (C) 2011 Elsevier By. All rights reserved.