Natural antimicrobials as food preservatives receive increasing attention due to improved consumer awareness about the influence of safe food and nutrition on human health, including a growing concern about microbial resistance towards conventional methods of food preservation. The source of natural antimicrobials is also Mentha piperita, which contains menthol, an important compound with extraordinary antimicrobial activity. The purpose of this thesis was initially to determine antimicrobial activity of various Mentha piperita preparations in vitro, by broth microdilution method. The preparation with a lowest minimal bactericidal concentration (0.89 μL/mL) was used in further studies to determine antimicrobial activity of Mentha piperita essential oil (MPEO) on beef stored for 5 days in a model experiment. Using standard microbiological methods, we found that the addition of MPEO inhibited the growth of all monitored indicator groups of bacteria (total aerobic mesophilic count, Enterobacteriaceae, and Salmonella) during storage. However, the addition of MPEO did not completely inhibit the growth of Salmonella and other bacteria, presumably due to the high inoculum and temperatures above 4-5 °C, which allowed Salmonella and other bacteria still to grow. The best antimicrobial effect of the MPEO was observed against Enterobacteriaceae, with 1.39 average log reduction.
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