D‑Value Calculator
Decimal Reduction Time – First‑order kinetics [citation:2][citation:7]
Decimal Reduction Time
D = t / log₁₀(N₀ / Nₜ)
where D = decimal reduction time, t = exposure time, N₀ = initial count, Nₜ = final count
D‑Value
—
minutes
at 121°C
Log reduction achieved
—
D‑values of Common Organisms [citation:2][citation:4]
| Organism | Temp (°C) | D‑value (min) | Medium |
|---|---|---|---|
| B. stearothermophilus | 121 | 1.5–3.0 | Water/glucose |
| C. botulinum | 121 | 0.2–0.3 | Phosphate buffer |
| C. sporogenes | 121 | 0.8–1.5 | Meat medium |
| B. subtilis | 121 | 0.5–0.8 | Water |
| E. coli | 60 | 0.5–1.0 | Culture medium |
D‑values vary with temperature, strain, and suspending medium [citation:2].
Interpretation [citation:7]
Higher D‑value = greater heat resistance. For sterilization, processes are designed to achieve 12‑log reduction of C. botulinum (12D concept).