Response surface models for effects of temperature and previous growth sodium chloride on growth kinetics of Salmonella typhimurium on cooked chicken breast

Abstract

Response surface models were developed and validated for effects of temperature (10 to 40°C) and previous growth NaCl (0.5 to 4.5%) on lag time (λ) and specific growth rate (μ) of Salmonella Typhimurium on cooked chicken breast. Growth curves for model development (n = 55) and model validation (n = 16) were fit to a two-phase linear growth model to obtain λ and μ of Salmonella Typhimurium on cooked chicken breast. Response surface models for natural logarithm transformations of λ and μ as a function of temperature and previous growth NaCl were obtained by regression analysis. Both λ and μ of Salmonella Typhimurium were affected (P < 0.0001) by temperature but not by previous growth NaCl. Models were validated against data not used in their development. Mean absolute relative error of predictions (model accuracy) was 26.6% for λ and 15.4% for μ. Median relative error of predictions (model bias) was 0.9% for λ and 5.2% for μ. Results indicated that the models developed provided reliable predictions of λ and μ of Salmonella Typhimurium on cooked chicken breast within the matrix of conditions modeled. In addition, results indicated that previous growth NaCl (0.5 to 4.5%) was not a major factor affecting subsequent growth kinetics of Salmonella Typhimurium on cooked chicken breast. Thus, inclusion of previous growth NaCl in predictive models may not significantly improve our ability to predict growth of Salmonella spp. on food subjected to temperature abuse.