Kill Step Validation Directions

Kill Step Validation Directions

Instructions for Use

  • D-value - Time required in minutes at a reference temperature to destroy 90% of an organism or its spores (equivalent to one log reduction).
  • Z-value - The number of degrees in temperature required to change the D value of a specific organism or its spores by 90% (equivalent to a factor of 10)
  • F-value – The process lethality or the time in minutes, at a specific temperature, required to destroy a certain number of viable cells.

Using the Calculator

  • Enter the Product & Process Specifications in cells D3–D9.
  • Download the temperature profile (time-temperature data) from a data logger to a blank Excel sheet.
  • Format the temperature profile (time-temperature data) for the specific product you collected so that the time is in one minute intervals.

*NOTE: Format the time so that you include at least the temperature data from 122°F/50°C during heating to the same temperature while cooling the product. It is acceptable to change the time intervals to larger values (such as ≥2 min) if the process is longer and the product is at 122°F/50°C for longer periods of time.

You NEED at least 20 time-temperature data points to accurately calculate the lethality of the process.

  • Copy and paste this time-temperature data to the Process Data table in the Baking Process Kill Step Calculator sheet. The minutes should be placed in the column labeled Time (m) and the temperature in the column labeled Core Temp.

Interpreting the Results

  • The cumulative “F value (min)” at the bottom of the “Process Data” table (cell C44) indicates the total lethality of the process at a reference temperature.
  • The process lethality (in terms of decimal reductions or log reductions) is indicated at the bottom of the “Process Data” (cell D44).
  • The total process lethality is summarized in the table “Process Lethality” (cell I-10).
  • The charts plot the time-temperature profile of the process, the F values of the process at different time points, and the cumulative log reductions achieved at each of the time points. 

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