Effect of essential oils of oregano and nutmeg on growth and surviavl of Staphylococcus aureus in barbecued chicken

In this study experiments were conducted to determine the effectiveness of oregano and nutmeg essential oils (Eos) on the growth and survival of Staphylococcus aureus in broth culture and in ready to use barbecued chicken. Samples were prepared with 1، 2، and 3 µl/g of oregano and nutmeg Eos. The test and control (without Eos) samples were inoculated with the bacteria to a final concentration of 7 log CFU/g and stored at 3، 8، and 20°C. Based on growth on Baird–Parker agar، bacteria was counted just before and at 24، 48، and 72h. In the broth culture system، the antibacterial activity of oregano (MIC=0. 62 µl/ml and MBC=0. 62 µl/ml) was superior than that of nutmeg (MIC=1. 25 µl/ml and MBC= 2. 5 µl/ml). In barbecued chicken، the log CFU/g of bacteria after up to 72 h of incubation was not decreased significantly by various combination of Eos and storage temperature when compared with control samples (without Eos). It is concluded that examination of Eos in broth system can yield accurate microbiological data، without complementary tests in foods these data are of limited value for assessing food safety.