Thermal Death of Microorganisms

A Heuristic Tutorial

NB: This is a work in progress. It is posted in this incomplete form so that anyone who may come across it will have the opportunity to send me comments or suggestions. The document will eventually be made interactive, with simple calculations, etc. Figures and charts will also be incorporated. I will add proper credits and references in due course. I hope this material will be an aid to understanding the various terms employed, properly or improperly, in the industry.

Please send comments or suggestions to Daniel Bull, Ph.D.

4. Some Common Measurements, or more accurately, Some Common Calculations. (TOC)

Now what? Well, for now, we’re going to ignore the rather disturbing fact that our model does not allow for complete killing of all organisms (except after infinite time!), and look at a few commonly used measurements, based on the assumption that the model is correct. This is actually a tenuous assumption at best, since many organisms do not die according to the first order kinetic model. This is especially true for spores, and is most pronounced at lower (but still lethal) temperatures. When it is true, it is usually for vegetative cells. More on this later.

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