Microbial Lethality
Compute the lethality rate (L-value) of a thermal process, L = 10^((T − Tref)/z), the factor indicating how many times faster (or slower) microbial destruction at a temperature T is than at the reference temperature. Integrated over time, the lethality gives the process F-value. It is the basis of the general-method sterilization calculation, which sums the lethality over the product's actual thermal history. Enter the temperature, the reference temperature and the z-value.
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Letalidade microbiana
A taxa de letalidade (valor L) responde: a uma temperatura T, a destruição microbiana é quantas vezes mais rápida (ou lenta) do que na temperatura de referência? L = 10^((T − Tref)/z). Por exemplo, com Tref = 121,1 °C e z = 10 °C, estar a 131,1 °C (10 °C acima) dá L = 10 — a morte é dez vezes mais veloz; a 111,1 °C, L = 0,1 — dez vezes mais lenta. A letalidade é a ferramenta do método geral de cálculo de processos térmicos: como a temperatura no ponto mais frio de uma lata varia durante todo o aquecimento e resfriamento, calcula-se L a cada instante e integra-se ao longo do tempo (∫L dt) para obter o valor F total acumulado do processo. Isso captura a esterilização real, incluindo a letalidade que acontece durante as fases de subida e descida de temperatura — não só no patamar. É mais preciso que os métodos de fórmula simplificados. Informe a temperatura, a temperatura de referência e o z.
Related Tools
F₀ Sterilization Value
Compute the F₀ value of a thermal process, F₀ = t·10^((T − 121.1)/z), the equivalent sterilization time at 121.1 °C (250 °F) with z = 10 °C, the reference for Clostridium botulinum. It is the universal 'currency' that compares thermal processes at different temperatures: an F₀ of 3 minutes is the minimum safety for low-acid canned foods (botulinum cook). Enter the time, the process temperature and the z-value.
Pasteurization Units (PU)
Compute the pasteurization units (PU) of a process, PU = t·10^((T − Tref)/z), the lethal time equivalent at a reference temperature. Widely used for beer and juice (Tref = 60 °C, z = 7 °C): a beer needs ~15 PU for microbiological stability. It lets you compare and control pasteurizers operating at different time-temperature combinations. Enter the time, the process temperature, the reference temperature and the z-value.
Decimal Reduction Time (D-Value)
Compute the decimal reduction time (D-value) of a microorganism, D = t/(log N₀ − log N), the time needed, at a given temperature, to destroy 90% of the population (a one-log reduction). It is the fundamental parameter of thermal death kinetics in food processing: the larger the D, the more heat-resistant the microorganism. Enter the heating time and the initial and final populations.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.