Final answer:
The decimal reduction time (DRT) or D-value is the time it takes to reduce a microbial population by 90%. It is a critical concept for evaluating the effectiveness of microbial control protocols like sterilization, which aims to completely kill all microbes.
Step-by-step explanation:
The decimal reduction time (DRT), also known as D-value, refers to the amount of time it takes for a specific microbial control protocol to produce a one order-of-magnitude decrease in the number of organisms, which equates to the death of 90% of the microbial population. Essentially, if you have 1,000 bacteria, a 1-D-value treatment would reduce the number to 100 bacteria, achieving a 90% reduction.
Microbial Control Protocols
Different microbial control protocols, such as sterilization, utilize the concept of D-value to quantify their effectiveness. Sterilization is the complete removal or killing of all vegetative cells, endospores, and viruses, which is different from protocols aimed at reducing the microbial load, including those measured by D-value. When plotting microbial death on a semilog plot, the line representing the decline of microbes due to the application of the control method will usually show a logarithmic relationship.
Factors Impacting Effectiveness
Several factors impact the effectiveness of a microbial control protocol, including the length of exposure to the disinfecting agent, concentration of the disinfectant, temperature, and presence of organic material. These variables must be considered along with the D-value to determine the appropriate application and expected outcome of a microbial control measure.