Objective: Staphylococcus aureus is one of the most prevalent causes of gastroenteritis worldwide. Knowing the precise boundary for the growth & no- growth interface of S. aureus and also determining the period of time needed for bacterial growth initiation is necessary for food safety risk assessment. Method & Materials: This study was designed to model the combined effects of different levels of Bonium persicum (black cumin) essential oil, temperature, hydrochloric acid and inoculum load on the growth of S. aureus in brain heart infusion broth. The growth was monitored by visible turbidity over 30 days. Results & Conclusion: The 108 measured data points showed significant effects of selected parameters on S. aureus growth. The experiment was carried out in triplicate. For data analysis, SAS statistical software- version 8.2 was employed and Stepwise Multiple Regression Program was used to predict the growth initiation. The model equation was as follows: TTD (Time to Detection) = 22.028 + 5.93 EO - 3.69 pH - 5.93 Temp- 3.42 IL. For obtaining a boundary model the logistic Regression Program was employed: Y (growth/no growth) = - [3.7396 + (4.23 EO) - (3.57 Temp) - (3.30 IL) - (2.71 pH)] The models adequately predicted the growth initiation and growth inhibition of S. aureus.

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