Chemical preservatives like benzoate and sorbate are used in food industry to prevent the growth of microorganisms in products such as mayonnaise. Due to concerns over the safety of some chemical preservatives in foods, we have done research to find safe and effective replacement. This study was to investigate the antibacterial properties of Thymus vulgaris leaves extract on home-made mayonnaise using Salmonella enteritidis, as a food pathogen. Moreover, the modeling behavior of this organism in mayonnaise, affected by T. vulgaris extract at 4oC and 25oC was investigated. Results showed that the reduction of S. enteritidis was depended on T. vulgaris extract concentration and storage temperature and it was higher for the mayonnaise that was kept at 25oC. This effect increased by increasing the concentration of extract. This test was evaluated as a completely randomized factorial design with three replications. These models are: Z=8.05-1.47x-0.15y-0.09xy+3.11x2+0.001y2, R2=0.98% and Z=9.24-0.22x-0.95y-0.48xy+0.024y2, R2= 0.8(Z: Log (cfu/g), x: concentration, y: time) for 4oC and 25oC respectively. Coefficient of determinations (R2>0.8) implies the validity of the proposed model. This investigation could help food industry to evaluate the effect of new preservatives, such as T. vulgaris, on the risk of pathogen growth and survival in mayonnaise.

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