Effects of Oregano Extract on the Inhibition of Selected Pathogens in Raw Beef Meat

Introduction: Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus have been found in raw meat and meat products. The present study aimed to evaluate the effects of oregano extract(OE) at the concentrations of 0.1%, 0.2%, and 0.5%against Listeria monocytogenes, Salmonella typhimurium, and Staphylococcus aureus in raw beef meat during refrigerated storage (4±1oC) for 10 days. Methods: In this study, 10 grams of raw beef meat were added to 90 milliliters of sterile buffered peptone water and homogenized in a stomacher for two minutes. Proper decimal dilutions were prepared in buffered peptone water for microbial enumeration. S. typhimurium was cultured on Salmonella Shigella agar and incubated at the temperature of 37oC for 24 hours. In addition, L. monocytogenes was cultured on PALCAM listeria-selective agar and incubated at the temperature of 30oC for 48 hours, and S. aureus was cultured on Baird-Parker agar and incubated at the temperature of 37oC for 48 hours. Results: In all the experiments, no growth was observed in L. monocytogenes, S. typhimurium, and S. aureus in the non-inoculated control samples. Antimicrobial effects were more significant at the higher concentrations of OE (P<0.05). Moreover, the addition of OEs to raw beef meat decreased the microbial counts of the tested pathogens during storage (P<0.05). Conclusion: According to the results, utilization of OE in raw beef meat may be an effectivestrategy to assure safety against L. monocytogenes, S. typhimurium, and S. aureus. However, the associated sensory limitations do not allow the use of OE at higher concentrations, which are more effective in pathogen inhibition.