Effects of Zataria multiflora Boiss. essential oil and nisin on Bacillus cereus ATCC 11778

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO, 0.0%, 0.005%, 0.015%, 0.03% and 0.045%) and nisin (N, 0.0, 0.25, 0.5, 1.5 and 2.5 mu g ml(-1)), pH values (7.4, 6.5 and 6.0), temperatures (Ts, 10, 20 and 30 degrees C) and storage times (Ds, up to 43 days) on log(10) probability percentage of growth initiation (logP%) of one vegetative cell of Bacillus cereus in brain heart infusion broth were evaluated in a factorial design study. The log P% of the organism was significantly affected (P < 0.01) by the values of EO, N, pH, T and D. The combinations of T >= 20 degrees C, EO <= 0.03%, and pH values (7.4, 6.5 and 6.0) could not obviously affect the growth of the organism in this study. Whereas, the strong inhibitory action was observed by increasing EO concentration to 0.045 at T >= 20 degrees C and selected pH values (7.4, 6.5 and 6.0) and by decreasing temperature to 10 degrees C at EO >= 0.01 51K and pH values used in this study. The inhibitory effect of N also was enhanced by decreasing storage temperature to 10 degrees C at the selected pH values (7.4, 6.5 and 6.0) in this study. The growth of the organisms was strongly affected by increasing EO concentration to 0.03% in combination with N concentrations used at the selected temperatures in this study. The growth of the organism was completely inhibited at combinations EO >= 0.015%, N >= 1.5 mu g ml(-1), T <= 30 degrees C and pH <= 7.4 during 43 days of storage in this study. This synergistic effect of EO and N was enhanced in lower pH values (6.5 and 6.0) in the present study. The growth of organism was completely inhibited at combinations of EO >= 0.005 and N >= 1.5 mu g ml(-1) at pH = 6.0, and EO >= 0.03 and N >= 0.5 mu g ml(-1) at pH <= 6.5 during the study at the selected Ts (30, 20 and 10 degrees C). (c) 2006 Elsevier Ltd. All rights reserved.