Efecto del aceite esencial del tomillo (Thymus Vulgaris), sobre el crecimiento de salmonella Enteritidis y salmonella Paratyphi en superficies de carne cruda bovina refrigerada.

Abstract

Essential oils (EO) are mostly phenyl-propane and terpene substances, which are stored in secretory tissues of the aromatic plant organs. It has been demonstrated antibacterial activity of various essential oils, which may contain more than 150 components. The antimicrobial action of thymol and carvacrol obtained from thyme (Thymus vulgaris), has been studied in order to control risks of contamination products. Most research in this area only address aspects of chemical composition and antimicrobial susceptibility testing but very few have explored the effect of EO applied directly as preservatives in foods and evaluated their joint action with temperature. In the present investigation, the effects of essential oil of thyme from two sources were evaluated: a commercial essential oil (EOc) and other extracted laboratory (EOe) on the growth of Salmonella Enteritidis and Salmonella Paratyphi on surfaces of raw meat refrigerated. The chemical composition of EO were analyzed by GC-MS and found that in EOc the predominant compounds were Thymol, p-Cymene and γ-Terpinene, while EOe predominant p-Cymene, Trans-β-Caryophyllene and Thymol. The antimicrobial activity was evaluated by agar diffusion method, finding that the two EOs showed significant effect in reducing S. Enteritidis and S. Paratyphi at all concentrations tested (10% - 50%). The minimum inhibitory concentration by the method of macro broth dilution showed that a higher concentration of EOc and EOe is required as to reduce the growth of S. Enteritidis what S. Paratyphi. Likewise, it requires more concentration than the EOc to reduce the two species of Salmonella evaluated. These results were also observed when three concentrations EOc and EOe (30%, 40% and 50%) on parts beef previously inoculated with 104 cfu / ml of the two species of Salmonella and maintained at 0°C, 4°C and 10°C for 72 hours. Results also showed that in vivo S. Paratyphi is more sensitive to the action of EO that S. Enteritidis, but its sensitivity seems to decrease with increasing temperature, otherwise observed with S. Enteritidis whose sensitivity to EO increased with decreasing the temperature. Independent of the result of effect of temperature, the EOc proved more effective than the reduction EOe two bacterial species in all cases showing a greater than 10% for S. Paratyphi concentration of 50% (v/v) and more than 7% at concentrations of 40 and 30% (v/v), this being significant variation at p <0.05. In contrast, the EOe presented at all concentrations reduced S. Paratyphi close to 6% not being significant at <0.05. As for S. Enteritidis, the reduction percentages were found near 4.5% for 0 and 4°C and 3.5% at 10°C for EOc and slightly more than 1% for the EOe. Although the percentages of low and narrow in some cases reduction, the application of EO thyme meat surfaces helps reduce the presence of Salmonella spp. in its surface, especially S. Paratyphi.