Survival of Clostridium botulinum Spores

Abstract

Radiation survival curves of spores of Clostridium botulinum strain 33A exhibited an exponential reduction which accounted for most of the population, followed by a "tail" comprising a very small residual number [7 to 0.7 spore(s) per ml] which resisted death in the range between 3.0 and 9.0 Mrad dose levels. The "tail" was not caused by protective spore substances released into the suspensions during irradiation, by the presence of accumulated radiation "inactivated" spores, or by heat shock of pre-irradiated spores. The theoretical number of spore targets which must be inactivated by irradiation was estimated both by a graphical and by a computation method to be about 80, and the D value was calculated to be 0.295 and 0.396 Mrad, respectively, in buffer and in pork pea broth.

Statistical Estimation of 12d for Radappertized Foods

“…It is usually assumed (Schmidt, 1963) that G(x) is of simple exponential form. There is some (perhaps inconclusive) evidence to support this assumption when the spores are in a model system (i.e., a transparent, fluid substrate), see e.g., Anellis et al (1965). In the critique of the Schmidt-Nank calculation we shall show evidence against the assumption when spores are in a food.…”

Radiation-Sterilization of Food: A Statistical Analysis

“…Different cans will have different Z p -values, hence Z n is a random variable, just as X is. The distribution and density functions associated with Z n are ( I> n (x), and 0 n (x), $ n (x) = Probability that Z p < x (4) 0 n (x) = d* n (x)/dx (5) Equation (4) means that ^(x) is the theoretical fraction of cans sterilized at dose x.…”