GIFSQ Tools · Module 3 — Food Microbiology & Enumeration · Tool 049 of 500
How fast a culture doubles. Enter the starting and final counts and the elapsed time to get the number of generations and the generation (doubling) time.
Try sample values — fills the form with the worked example below.
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Generations
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Generation time (min)
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Generation time (h)
Equation: generations n = log₂(N ÷ N₀) = (log N − log N₀) ÷ log 2 · generation time g = t ÷ n, where t is the elapsed time.
Method: Exponential-growth model, standard food microbiology (FDA BAM growth concepts; Brock Biology of Microorganisms). Generation time is the doubling time in the exponential (log) phase.
Assumptions: growth is exponential over the measured interval (log phase); temperature and nutrients stay constant; no lag phase inside the interval.
Limitations: the model does not apply during lag phase or stationary phase; one interval gives an average rate only, not the rate at any single moment.
Rounding: generations and generation time to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: Exponential-growth model, standard food microbiology (FDA BAM growth concepts; Brock Biology of Microorganisms). Generation time is the doubling time in the exponential (log) phase.
Assumptions: growth is exponential over the measured interval (log phase); temperature and nutrients stay constant; no lag phase inside the interval.
Limitations: the model does not apply during lag phase or stationary phase; one interval gives an average rate only, not the rate at any single moment.
Rounding: generations and generation time to 2 decimal places; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: A culture grows from 1,000 to 16,000 cells in 120 minutes. Generations = log₂(16) = 4; generation time = 120 ÷ 4 = 30 minutes (0.50 h).
Enter values above to see results.
Generation times for common food bacteria at warm temperatures are often 20 to 60 minutes; cold storage stretches them to hours or days. The result applies to the log phase only. Tool 049 of 500 — GIFSQ
