D-VALUE

Many kinds of microbes are pathogens, meaning they are capable of causing disease to other organisms. Sterilization processes, such as exposure to heat, destroy these pathogens. D-value refers to decimal reduction time - The time required at a certain temperature to kill 90% of the organisms being studied. Thus after an organism is reduced by 1 D, only 10% of the original organisms remain. The population number has been reduced by one decimal place in the counting scheme. Generally, each lot of a sterilization-resistant organism is given a unique D-value. When referring to D values it is proper to give the temperature as a subscript to the D. For example, a hypothetical organism is reduced by 90 fter exposure to temperatures of 300 degrees Fahrenheit for 2 minutes, Thus the D-value would be written as D300F = 2 minutes. D-value determination is often carried out to measure a disinfectant's efficiency to reduce the number of microbes, present in a given environment.
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