D-value

D-value is a term used in microbiology to denote the time required at a certain temperature to kill 90% of the organisms being studied. This concept is particularly important in the field of food preservation and sterilization. The D-value is a measure of the thermal resistance of a microorganism.

Definition

The D-value is defined as the time (in minutes) required to kill 90% of a population of the organism under specified conditions. It is a measure of the thermal resistance of a microorganism. The D-value is used in calculations to determine the necessary time and temperature needed to kill a specific number of microorganisms.

Calculation

The D-value is calculated using the following formula:

D = t / log(N0/N)

where:

• t is the time of heat treatment
• N0 is the initial number of viable organisms
• N is the number of viable organisms after heat treatment

Factors affecting D-value

The D-value can be affected by several factors, including:

• The species and strain of the microorganism
• The age of the microorganism
• The environment in which the microorganism is found
• The temperature and time of the heat treatment

Applications

The D-value is used in various fields, including:

• Food preservation: The D-value is used to determine the necessary time and temperature needed to kill a specific number of microorganisms in food products.
• Sterilization: The D-value is used in the sterilization of medical equipment and other materials to ensure that they are free of microorganisms.

See also

• Z-value
• F-value
• Thermal death time