When a fixed sterilization temperature is used, which statement about initial contamination is generally correct?

• A. The greater the initial contamination, the longer the time necessary to kill all organisms
• B. The greater initial contamination, the shorter the time necessary to kill all organisms
• C. The smaller the initial contamination, the longer the time necessary to kill all organisms
• D. The exposure length is of no significance in the processing procedure

Answer: (A)

At a fixed sterilization temperature, the rate at which organisms are killed is determined by the temperature and the organism, not by how many are present. What changes with higher initial contamination is how long you must apply the exposure to reach the same level of sterility. The total kill you aim for is a fixed log reduction, so the time required is proportional to the log of the initial population. Using the idea that N(t) decreases roughly logarithmically at a given temperature, you can think of it as t being proportional to log10(N0/NF), where NF is the target final population (often a very small number or nearly zero survivors). Thus, larger N0 means longer time to reach the same sterility level. The exposure length is indeed significant because insufficient time won’t achieve the desired reduction, while the same temperature and process conditions apply.