The kill step calculator allows bakers to monitor food safety inside the oven.

The kill step calculator allows bakers to monitor food safety inside the oven, while compiling with the FDA mandated FSMA.

Kill Step Calculator 

What is a Kill Step Calculator?

The Kill Step Calculator is a tool bakeries can use to validate the effectiveness of kill-steps during production. The new FDA mandated FSMA (117.160) requires validation and verification of the kill-step.1

A kill-step is necessary to eliminate harmful pathogens such as Salmonella spp. in bakery ingredients and products. Proper monitoring of oven temperatures using the Kill Step Calculator will allow bakeries to comply with FSMA (117.160). 2


The Kill Step Calculator was developed by AIB International in cooperation with Kansas State University, American Bakers Association, and the University of Georgia.  The Kill Step Calculator procedure and calculator can be downloaded from AIB.

The user must have access to Excel software and a data logger. Kill Step Calculators currently exist for the following items:

  • Hamburger buns
  • Basic round top cake muffins
  • Nut Muffin
  • 100% whole wheat multigrain bread
  • Crispy Cookies
  • Soft Cookies
  • Doughnut

How does it work?

Oven temperatures are monitored using a 6 temperature point probe (data logger) that is placed into a baked good. Temperatures are recorded at 15 second intervals by the data logger. The process should be monitored at least 5 times. After the final run, all oven temperatures from the data logger are downloaded into an Excel spread sheet and analyzed.

The data points that took the longest amount of time to reach 170oF should be selected for analysis in the Process Lethality Fahrenheit Tab (Process Lethality Celsius if using Celsius) of the Kill-Step Calculator. Twenty points of data for time and temperature are needed for proper analysis.

Once the data is imported into the Kill-Step Calculator, Process Lethality will automatically be calculated.

The following video tutorial is available for a quick overview of the process:

How to use it

Here are the steps for using the Kill Step Calculator3:
(The following example is for buns and it can be found here)

A: Identify the Coolest Oven Zone

  • Using a data logger, setup a test run following the protocol outlined in Step 2 of the Procedure for Recording Temperature Profiles in a Commercial Oven.
  • Run three replicates for each position in the oven, instead of five replicates
  • Example 1: If there are four lanes of pans, then three replicates will be run at each of the lanes.
  • Example 2: In a revolving oven on Shelf 1 with six pan positions, run three replicates at each of the six pan positions.
  • The position that requires the longest time to reach an internal bun temperature of 170°F (77°C) would be the cool zone.

B: Step 1: Format the Data Logging Device

  • Prepare the data logging device for use by setting to record temperatures at a frequency of every 15 seconds or adjust the time interval as per the baking time.
  • Select either °F or °C for recording temperatures. The final calculator is equipped to convert between these values.
  • Refer to your device’s quick start manual for detailed instructions on preparing your specific logging device.

C: Step 2: Placement of Data Logger

  • Select a pan of buns that has just completed the proofing cycle and is ready to enter the oven and travel in the cool zone.
  • Hold the pan for placement of the data logger.
  • Place the data logger directly on top of the buns in the last row and center column of the pan
  • Stretch the six thermocouple wires to the row of buns that is farthest from the data logger, concentrating the probes toward the center lane of the pan (see Figure 1).
  • Begin by inserting probe 1 in the bun in the farthest left column and working through, probe by probe, until reaching the bun column farthest to the right.
  • For pans containing fewer than 6 columns, place any additional probes in the buns closest to the center line of the pan.
  • When inserting the probes, pierce through the sidewall of the bun, and be careful to insert the tip of the probe as close to the geometric center of the bun as possible.
Kill step calculator

Figure 1

  • Once the probes have been set, follow your data logger device’s specific procedures to start recording and close the box lid.
  • Let the pan continue to travel through the coolest oven zone and retrieve after the baking cycle is complete.
  • Follow the device instructions for removing probes and ending recording.
  • Download the recorded data to a computer and prepare the data logger for another run.
  • Export the data from each run into Excel format and save for later use. For quick reference, save each run under a new tab in the same Excel worksheet.
  • Repeat this process until data from a total of five product runs has been recorded.

D: Step 3: Data Compilation and Oven Validation

  • Determine which probes took the longest amount of time to reach 170°F (77°C) for each run by using the Excel files.
  • Converting the Excel data into graphical format allows for easier selection of the coolest probes. In Excel, highlight the entire data series for all six probes, select the Insert tab and click on Insert Line Chart icon. A graph will display next to the data columns on the worksheet. The lowest line represents the coolest sensor (time along x-axis, temperature along y-axis).
  • Copy and paste the column of data for the coolest sensor across all five runs into the appropriate Baking Process Kill Step Calculator tab.

E: Step 4: Analyze Process Lethality

  • Copy and paste at least 20 time-temperature data results 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.
  • Total process lethality for Salmonella should be greater than a 5 log reduction.


  1. “FSMA Final Rule for Preventive Controls for Human Food.” FSMA Final Rule for Preventive Controls for Human Food. US Food and Drug Administration, 16 Sept. 216.
  2. Channaiah, Lakshmikantha. “January/ February By Lakshmikantha Channaiah Building Effective Food Safety Systems.” Jan.-Feb. 2016: 21-23. JSTOR.
  3. “Baking Process Kill Step Calculators – Empowering Bakeries to Validate Their Food Safety Preventive Controls.”AIB International. AIB, n.d.
  4. “Hamburger Bun Kill Step Calculator Instructions” AIB International.