Define the D-value in thermal processing.

Define the D-value in thermal processing.

• A. The time at a specific temperature to achieve a 1-log (90%) reduction of the target organism
• B. The duration of pasteurization exposure
• C. The temperature change required to change the D-value by tenfold
• D. The temperature at which the organism is completely inactivated

Answer: (A)

In thermal processing, the D-value is the time required at a specific temperature to achieve a one-log reduction (a 90% decrease) in the target microorganism. It shows how resistant the organism is under those exact conditions and is specific to both the organism and the food matrix. For example, if at a chosen temperature the D-value is 12 seconds, holding at that temperature for 12 seconds reduces the population by 90%; 24 seconds would reduce by 99% (two logs), and so on. The D-value changes with temperature, and the way it changes is described by the z-value, which is the temperature change needed to change the D-value by tenfold. It’s not the total duration of pasteurization, nor a temperature to completely inactivate the organism, but a fixed time at a fixed temperature that yields a fixed level of reduction.

In thermal processing, the D-value is the time required at a specific temperature to achieve a one-log reduction (a 90% decrease) in the target microorganism. It shows how resistant the organism is under those exact conditions and is specific to both the organism and the food matrix. For example, if at a chosen temperature the D-value is 12 seconds, holding at that temperature for 12 seconds reduces the population by 90%; 24 seconds would reduce by 99% (two logs), and so on. The D-value changes with temperature, and the way it changes is described by the z-value, which is the temperature change needed to change the D-value by tenfold. It’s not the total duration of pasteurization, nor a temperature to completely inactivate the organism, but a fixed time at a fixed temperature that yields a fixed level of reduction.