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Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/11/2015 Publication Date: 12/4/2015 Citation: Huang, L. 2015. Growth of Staphylococcus aureus in cooked potato and potato salad – A one-step kinetic analysis. Journal of Food Science. 80(12):M2837-44. doi: 10.1111/1750-3841.13110. Interpretive Summary: Staphylococcus aureus is a foodborne pathogen capable of producing heat-stable enterotoxins that cause acute gastrointestinal diseases. Potato salad is a frequent vehicle for infection and food poisoning caused by S. aureus. This study investigates the growth of this pathogen in cooked potato and potato salad to develop mathematical models to describe and simulate its growth under different temperature conditions. The models developed in this can accurately predict the growth of S. aureus in cooked potato and potato salad and can be used in risk assessment of this microorganism. Technical Abstract: Staphylococcus aureus is a Gram-positive spherically-shaped bacterium capable of producing heat-stable enterotoxins that cause acute gastrointestinal diseases. The growth of this pathogen in food is a major threat to public health worldwide. Potato salad is a frequent vehicle for infection and food poisoning caused by S. aureus. Therefore, the objective of this study was to investigate the growth kinetics of S. aureus in cooked potato and potato salad. Samples of potato cubes and potato salad inoculated with S. aureus were incubated at temperatures between 8 and 43 Deg. C to observe its growth for developing growth models. No growth was observed at 8 Deg. C. The experimental results showed that the growth curves did not exhibit lag phases, and can be described by a three-parameter logistic model. A one-step kinetic analysis approach was used to simultaneously analyze all growth curves by direct construction of both the primary and secondary (Ratkowsky square-root) models using nonlinear regression to minimize the global residual error. The estimated nominal minimum growth temperature of S. aureus was 6.12 Deg. C in potato cubes and 8.80 Deg. C in potato salad. The estimated maximum growth temperatures of S. aureus in potato cubes and potato salad were very close to each other (46.3 and 46.8 Deg. C, respectively). On the average, the specific growth rates of S. aureus in potato cubes were approximately 70% higher than those in potato salad. This study suggests that cooked potato and potato salad should be stored below 6 Deg. C or above 47 Deg. C to prevent the growth of S. aureus. The mathematical models and kinetic parameters can be used to accurately evaluate the effect of temperature abuse on the growth of S. aureus and conduct risk assessments of S. aureus in cooked potato and potato salad. |
