Thermal inactivation kinetics of mixed microbial populations. A hypothesispaper

The authors have investigated inactivation kinetics of mixed microbial popu lations, which consist of component subpopulations following first-order in activation kinetics. Populations which had undergone previous partial heat treatment were also included in the study. As the survivor ratio is the Lap lace transform of the rate constant distribution an analysis of survival fu nctions following nth-order inactivation kinetics (n > 1) resulted in a gam ma distribution of the first-order rate constants. The expected value of th e gamma distribution is proportional to the resulting nth-order rate consta nt and inversely proportional to the nth-order time constant. According to the theory, the nth-order time constant and survivor ratio are independent of the initial microbial concentration. The temperature effect has been tre ated with the restriction that a monotonously increasing functional relatio nship exists between first-order rate constants at two different temperatur es. This monotonous function relates first-order rate constants of the same subpopulation. The Laplace transformation method is applicable to create a nalytical functions for fitting them to measured semilogarithmic survivor c urves, if these curves are of the concave type. (C) 1999 Elsevier Science L imited. All rights reserved.