Microbiological process discussion. Ph function in food process calculations.

Depending upon the contours, or profiles, of relationships between time and temperature applying (a) to the destruction of offensive organisms at constant temperature and (b) to the temperature change to which food is subjected, and depending upon the particular mathematical forms used to express these relationships, there are at-least two parameters associated with each relationship-a velocity index or coefficient, and a location index. The location index might be called an index of intensity. If either relationship has irregular characteristics which would complicate its mathematical expression, more than two parameters may be utilized to define that relationship. Hundreds of different patterns of each of these relationships are usable and, for each of these, various forms of mathematical expression can be employed. For example, the exponential thermal destruction-time relationship for microorganisms may be equally well expressed in any of the following three forms (among other forms):