New mathematical modeling approach for predicting microbial inactivation by high hydrostatic pressure

Area of Science:

• Microbiology
• Food Science
• Biophysics

Background:

• Bacterial inactivation kinetics under pressure are often non-log-linear.
• Existing models may not fully capture complex inactivation patterns.

Purpose of the Study:

• To develop a new primary model for non-log-linear inactivation kinetics of pressure-treated bacteria.
• To describe the relationship between inactivation rate and time.
• To enable calculation of processing parameters and thermodynamic insights.

Main Methods:

• A thermodynamically consistent first-order kinetic approach was used.
• The model assumes the specific inactivation rate is inversely proportional to the square root of time.
• The model was tested against experimental data and 138 published data sets.

Main Results:

• The model provided reasonable fits to experimental data over 6-7 orders of magnitude.
• Good fits were achieved for approximately 70% of published data with a convex upward curve.
• The model successfully accommodated curves with shoulder and tail regions using additional parameters.
• Model parameters showed regular variation with pressure, suggesting a mechanistic basis.
• Parameters analogous to thermal processing D and z values were calculated.
• Apparent thermodynamic volumes of activation for lethal events were determined.

Conclusions:

• The new model accurately describes non-log-linear bacterial inactivation kinetics under pressure.
• The inverse square root time dependency suggests a diffusion-limited inactivation process.
• The model facilitates the prediction of inactivation and optimization of processing conditions.