7. In for the Kill.  (TOC)

Let’s assume that we have a solution of some sort of organic material that we want to sterilize. That is, we want to reduce the number of viable organisms in the solution to zero. Recall from the introduction that the analogy drawn between destruction of microorganisms and first order chemical kinetics leads to the realization that the approach is probabilistic. When we deal with a collection of microorganisms, even a pure culture, we cannot say with certainty whether the solution will be sterile after a given heat treatment. That is, we cannot conclude that there are no surviving organisms. Our equations describe the enumeration of the surviving organisms as a fraction of the original number which survive. Probability descriptions lose meaning when dealing with a very small number of surviving organisms. It is nonsense to speak of, say, half of an organism surviving.