Equivalent Isothermal Time at a Reference Temperature as a Function of Time

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This fifth of five Demonstrations depicts the change in the equivalent isothermal time versus the process time (in minutes) for a chosen temperature history and reference temperature. The equivalent isothermal time is the time at the selected reference temperature that will produce the same degree of inactivation as the chosen process. This is done by setting eight temperature profile parameters, three Weibullian heat resistance parameters, and the isothermal reference temperature. Notice the automatic scaling of the axis; it is different in each example.

Contributed by: Mark D. Normand and Micha Peleg (March 2011)
Open content licensed under CC BY-NC-SA



This is the fifth of five Demonstrations of functions used to model thermal processing of foods for the purpose of eliminating the presence of pathogenic and spoilage microorganisms. The five Demonstrations allow slider-control manipulation of the plots of:

1) an 8-parameter nonlinear "temperature profile", temperature (in degrees C) versus time (in minutes)

2) a 2-parameter nonlinear Weibullian rate, , as a function of temperature (in degrees C)

3) a 10-parameter nonlinear Weibullian rate, , as a function of time (in minutes)

4) an 11-parameter dynamic microbial log survival, , as a function of time (in minutes)

5) a 12-parameter equivalent isothermal time as a function of time (in minutes)

Please note that not all possible parameter combinations yield a realistic temperature profile and corresponding equivalent time curve.

Snapshot 1: pasteurization

Snapshot 2: low temperature sterilization

Snapshot 3: insufficient heat process

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