GIFSQ Tools · Module 17 — Food Processing, Thermal Engineering & Utilities · Tool 321 of 500
Calculate the sterilisation value F₀ of a thermal process from the holding temperature, holding time and z-value, using the Bigelow method — for low-acid canned foods and retort processes.
Try sample values — fills the form with the worked example below.
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F₀ value (min)
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Lethal rate (L)
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Of target F₀ (%)
Equation: Lethal rate L = 10^((T − 121.1) / z); F₀ = t × L, where T is the holding temperature in °C, t the holding time in minutes, and z the temperature change for a tenfold change in death rate.
Method: Bigelow method for thermal process lethality, reference temperature 121.1 °C, as used under FDA 21 CFR 113 (thermally processed low-acid foods) and 21 CFR 114 (acidified foods); see also the IFT/FDA BAM thermal processing references.
Assumptions: the holding temperature is constant for the whole holding time; the target organism has a single z-value over the range used; come-up and cooling lethality are not included.
Limitations: this is a single-temperature estimate, not a full heat-penetration study; real processes need measured cold-point temperatures and a validated scheduled process.
Rounding: F₀ to 2 decimal places, lethal rate to 3, percent of target to 1; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value. A calculated lethality is an estimate only — a scheduled process must be established by a qualified process authority; never present this calculation as a validated process.
Method: Bigelow method for thermal process lethality, reference temperature 121.1 °C, as used under FDA 21 CFR 113 (thermally processed low-acid foods) and 21 CFR 114 (acidified foods); see also the IFT/FDA BAM thermal processing references.
Assumptions: the holding temperature is constant for the whole holding time; the target organism has a single z-value over the range used; come-up and cooling lethality are not included.
Limitations: this is a single-temperature estimate, not a full heat-penetration study; real processes need measured cold-point temperatures and a validated scheduled process.
Rounding: F₀ to 2 decimal places, lethal rate to 3, percent of target to 1; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value. A calculated lethality is an estimate only — a scheduled process must be established by a qualified process authority; never present this calculation as a validated process.
Worked example: Holding at 121.1 °C for 3 min with z = 10 °C: L = 10^0 = 1, F₀ = 3.00 min, 100.0% of a 3 min target.
Enter values above to see results.
The common commercial-sterility target for low-acid canned foods is F₀ = 3 min (12D for C. botulinum); your scheduled process sets the real target. Tool 321 of 500 — GIFSQ
