GIFSQ Tools · Module 3 — Food Microbiology & Enumeration · Tool 052 of 500
Work out how much inoculum each sample needs, how many samples a challenge study needs, and the total inoculum to prepare.
Try sample values — fills the form with the worked example below.
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Inoculum per sample (mL)
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Total samples
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Total inoculum (mL)
Equation: Inoculum volume per sample = (target level × sample size) ÷ stock concentration; total samples = time points × replicates + spares; total inoculum = volume per sample × total samples.
Method: Challenge-study inoculum planning per ISO 20976-1:2019 (challenge tests for growth potential) and FDA BAM guidance on inoculated-pack studies; target levels of 10³–10⁵ CFU/g are typical for growth-potential work.
Assumptions: The inoculum mixes evenly through the sample, the stock concentration is known, and each sample receives the same volume.
Limitations: A volume below 0.1 mL is hard to pipette accurately — dilute the stock first. This planner does not set the sampling schedule or the pass criteria; those come from the study protocol.
Rounding: Volumes to 3 decimal places (4 where below 0.01 mL); sample counts are whole numbers; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Method: Challenge-study inoculum planning per ISO 20976-1:2019 (challenge tests for growth potential) and FDA BAM guidance on inoculated-pack studies; target levels of 10³–10⁵ CFU/g are typical for growth-potential work.
Assumptions: The inoculum mixes evenly through the sample, the stock concentration is known, and each sample receives the same volume.
Limitations: A volume below 0.1 mL is hard to pipette accurately — dilute the stock first. This planner does not set the sampling schedule or the pass criteria; those come from the study protocol.
Rounding: Volumes to 3 decimal places (4 where below 0.01 mL); sample counts are whole numbers; intermediates unrounded.
This is a calculation aid, not a laboratory report — confirm against your accredited method before citing a value.
Worked example: Stock 1.0 × 10⁷ CFU/mL, target 10,000 CFU/g, 25 g samples, 5 time points × 3 replicates: volume per sample = (10,000 × 25) ÷ 10⁷ = 0.025 mL; 15 samples; total inoculum 0.375 mL.
Enter values above to see results.
Confirm the target level, strains and sampling times in the approved study protocol before inoculating. Tool 052 of 500 — GIFSQ
