z-Value (Thermal Resistance)
Compute a microorganism's z-value, z = (T₂ − T₁)/(log D₁ − log D₂), the temperature change needed to alter the D-value (decimal reduction time) by a factor of 10. The z measures the microorganism's temperature sensitivity: the smaller the z, the more the destruction accelerates with heating. It is the basis of converting between processes at different temperatures (F₀, pasteurization). Enter two temperatures and their corresponding D-values.
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Valor z (termorresistência)
Enquanto o valor D descreve a morte microbiana numa temperatura fixa, o valor z = (T₂ − T₁)/(log D₁ − log D₂) descreve como o D muda com a temperatura. Especificamente, z é o quanto a temperatura precisa subir para o D cair a um décimo — ou seja, para a destruição ficar 10× mais rápida. Um z pequeno (ex.: 7 °C, típico de células vegetativas e leveduras) significa que a morte acelera dramaticamente com pouco aumento de temperatura — a base da pasteurização rápida (HTST). Um z grande (ex.: 10 °C, esporos bacterianos) significa que é preciso subir bastante a temperatura para acelerar a morte, exigindo a esterilização a 121 °C. O z é o que permite construir o F₀ e converter processos entre temperaturas: graficamente, é a inclinação da 'curva de morte térmica' (log D vs T). Informe duas temperaturas e seus valores D.
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