Final answer:
The two methods of determining lethal limits of time and temperature are the microbial death curve and the median lethal dose.
Step-by-step explanation:
Two methods of determining lethal limits of time and temperature are the microbial death curve and the median lethal dose.
1. Microbial death curve: This curve describes the progress and effectiveness of a microbial control protocol. It plots the percentage of microbes killed over time, with the reduction typically being logarithmic. The time it takes for a specific protocol to produce a one order-of-magnitude decrease in the number of organisms, or the death of 90% of the population, is called the decimal reduction time (DRT) or D-value.
2. Median lethal dose: This method involves conducting controlled experiments with laboratory animals to determine the amount of pathogen cells or virions that can kill 50% of the infected animals. The LD50 value represents the concentration required to achieve this lethal effect.