ABSTRACT
The growing interest in substitution of chemical food preservatives, both antimicrobials and antioxidants, by natural ones has fostered research on the vegetable sources and screening of plant extracts and essential oils in order to identify acceptable natural alternatives. In order to evaluate the antimicrobial effects of different essential oils on food-borne pathogens and/or food spoilage microorganisms, first we should study them in laboratory models and then in foods. In this study Log probability percentage of growth [Log P%] of Bacillus cereus in Brain Heart Infusion broth as affected by different concentrations of Zataria multiflora Boiss. essential oil [0.0, 0.005, 0.015, 0.03 and 0.045%] during 43 days of storage at three different temperatures [30,20 and 10°C] was investigated. The Log P% of B. cereus was affected significantly [p < 0.05] by different concentrations of the essential oil, storage temperatures and combined effects of them. The maximum Log P% of B. cereus [and the day to reach the maximum probability of growth] in BHI broth with 0% essential oil at 30, 20 and 10°C were 1.46 [1], 1.46 [3] and 0.15 [28], respectively. While in BHI broth with 0.005, 0.015, 0.03 and 0.045% essential oils were 1.46 [1], -1.4693 and -3.54 [22]; 1.46 [1], 1.46 [10] and -3.85 [25]; 1.46 [16], 1.46 [16] and -4.45 [>43] and 0.15 [13], -1.85 [7] and -4.54 [>43], respectively. According to our results the Log P% of B. cereus was significantly decreased [P<0.05] by little increase of essential oil concentrations in this study. This inhibitory effect of the essential oil was also significantly increased [P<0.05], when the temperature decreased and we did not observe any growth [Log P% = -4.54] in broth with 0.03 and 0.045% essential oil during 43 days storage at 10°C