Atividade antimicrobiana de óleos essenciais frente à Salmonella enterica Enteritidis inoculada em carne moída bovina

Abstract

Was studied the antimicrobial effect of essential oils of oregano (Origanum vulgare) and lemongrass (Cymbopogon citratus) against Salmonella enterica Enteritidis S64 in vitro and inoculated in ground beef under refrigeration during six days of storage. It was found the action of these oils also on the accompanying microbiota, in the last day of storage. The essential oils were extracted by hydrodistillation in a modified Clevenger apparatus, and in vitro test was done based on the method of Agar Diffusion cavity. Was obtained thus the Minimum Inhibitory Concentration (MIC) that was equal to 0.39% v/v for the two oils. From this result, it was stipulated the minimum and maximum concentration for the treatment of samples of ground beef inoculated with Salmonella enterica Enteritidis S64 in concentration of 105 CFU /g, stored for 6 days under refrigeration (7ºC). On days 0, 1, 2, 4 and 6 days of storage, microbiological tests were performed to quantify the population of Salmonella in meat and remaining associated with the antimicrobial effect of the oils. In parallel was observed the evolution of psychrotrophic microorganisms in a control sample (without oil and without inoculum) and the effect of oils on psychrotrophic microorganisms on the sixth day of storage on meat inoculated with Salmonella. Both oils were effective in reducing the pathogen population and psychrotrophic microorganisms. Concentrations of 1.56% and 3.125% v/w oil lemongrass showed bactericidal activity 100% against Salmonella, soon in the first hours of contact (time 0). But the oil of oregano has achieved the same result with one day of storage at a concentration of 3.125% and 1.56% for four days. The largest reduction of psychrotrophic microbiota was achieved by treatment with oregano concentration 3.125% v/w, which although not eliminate altogether, achieved the largest reduction (5.19 Log CFU).