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Staphylococcus aureus growth boundaries: moving towards mechanistic predictive models based on solute-specific
Cynthia M Stewart1, Martin B Cole, J David Legan
1Nabisco, Inc., East Hanover, New Jersey 07936, USA. cindy.stewart@foodscience.afisc.csiro.au
Applied and Environmental Microbiology
|March 28, 2002
Summary
Understanding Staphylococcus aureus growth boundaries is key for food safety. This study modeled how humectants, pH, and potassium sorbate affect bacterial growth in intermediate-moisture foods.
Area of Science:
- Food Microbiology
- Food Safety Engineering
- Predictive Microbiology
Background:
- Shelf-stable intermediate-moisture foods pose food safety challenges.
- Accurate Staphylococcus aureus growth boundary data is crucial for risk assessment.
Purpose of the Study:
- To investigate the impact of humectants on Staphylococcus aureus growth boundaries.
- To develop predictive models for Staphylococcus aureus growth in intermediate-moisture foods.
Main Methods:
- Evaluated effects of relative humidity (RH), pH, and potassium sorbate on S. aureus growth.
- Assessed humectant properties like glass transition temperature and membrane permeability.
- Monitored growth via turbidity and toxin production over 24 weeks.
- Analyzed 1,792 data points using LIFEREG procedures.
Main Results:
- All tested parameters (humectants, RH, pH, potassium sorbate) significantly influenced S. aureus growth.
- Different humectants created distinct growth-no-growth boundaries.
- Sucrose/fructose inhibited growth most at neutral pH; NaCl was most inhibitory at low pH.
- Potassium sorbate significantly expanded no-growth zones, especially at pH < 6.0.
Conclusions:
- Humectant choice critically impacts S. aureus growth boundaries in intermediate-moisture foods.
- Developed models provide valuable tools for food safety risk assessment.
- Findings highlight the importance of considering solute properties and interactions in predictive modeling.