GIFSQ Tools · Module 17 — Food Processing, Thermal Engineering & Utilities · Tool 322 of 500
Calculate the F-value of a heat treatment at any reference temperature — for pasteurisation, blanching and other processes where the reference temperature is not 121.1 °C.
Try sample values — fills the form with the worked example below.
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F-value (min)
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Lethal rate (L)
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Log reduction
Equation: Lethal rate L = 10^((T − Tref) / z); F = t × L; log reduction = F ÷ D, where Tref is the reference temperature, t the holding time in minutes and D the decimal reduction time at Tref.
Method: Bigelow F-value method, generalised to any reference temperature, as used for pasteurisation and blanching schedules under FDA 21 CFR 113/114 and IFT thermal processing guidance.
Assumptions: the holding temperature is constant; a single z-value and D-value describe the target organism over the range used; come-up and cooling lethality are not included.
Limitations: D- and z-values are organism- and product-specific and must come from validated data; this tool does not supply them.
Rounding: F-value and lethal rate to 3 decimal places, log reduction to 2; 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 F-value method, generalised to any reference temperature, as used for pasteurisation and blanching schedules under FDA 21 CFR 113/114 and IFT thermal processing guidance.
Assumptions: the holding temperature is constant; a single z-value and D-value describe the target organism over the range used; come-up and cooling lethality are not included.
Limitations: D- and z-values are organism- and product-specific and must come from validated data; this tool does not supply them.
Rounding: F-value and lethal rate to 3 decimal places, log reduction to 2; 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: Milk held at 72 °C for 15 s (0.25 min) against a 71.7 °C reference with z = 7.5 °C and D = 0.5 min: L = 1.096, F = 0.274 min, log reduction = 0.55.
Enter values above to see results.
HTST milk pasteurisation (71.7 °C for 15 s) is the classic reference case; change Tref, z and D for other organisms and products. Tool 322 of 500 — GIFSQ
