Nature of the inactivation curves of Bacillus Pumilus spores heated using non‐isothermal and isothermal treatments

Isothermal and non-isothermal heat resistance studies were carried out on Bacillus pumilus spores. The non-isothermal study revealed a non-linear behavior of the survivor curve, which was revealed as a tail after an isothermal study. Results indicated that the spores obtained by isolating cells from colonies of the tail section were more heat resistant than the original ones (D104°c= 0.15 and 1.9 min for spores from the original population and from the tail, respectively). Application of the Weibull distribution model to analyze the tail produced good results at the 3 temperatures studied. Nevertheless, when the model was applied to curves having both concave downward and concave upward sections a poor result was obtained, with an accuracy factor greater than 1.