Combined application of essential oils from Origanum vulgare L. and Rosmarinus officinalis L. to inhibit bacteria and autochthonous microflora associated with minimally processed vegetables

AbstractThis study assessed the occurrence of an enhancing inhibitory effect of the combined application of Origanum vulgare (OV) and Rosmarinus officinalis (RO) essential oils against bacteria associated to minimally processed vegetables using the determination of Fractional Inhibitory Concentration (FIC) index, kill-time assay in vegetal broth and application in vegetable matrices. Moreover, it was determined chemical composition of the essential oils and their effects alone and in mixture on sensory characteristics of minimally processed vegetables. Carvacrol (66.9g/100g) was the most prevalent compound in OV essential oil, while for RO was 1.8-cineole (32.2g/100g). OV and RO essential oil showed MIC in a range of 1.25–5 and 20–40μL/mL, respectively. FIC indices of the combined application of the essential oils were 0.5 against Listeria monocytogenes, Yersinia enterocolitica and Aeromonas hydrophilla suggesting a synergic interaction. Only for Pseudomonas fluorescens FIC index was 0.75 purposing additive effect. Application of the essential oils alone (MIC) or in mixture (¼ MIC+¼ MIC or ¼ MIC+½ MIC) in vegetable broth caused significant decrease (p<0.05) in bacterial count over 24h. Mixture of essential oils reduced (p