Risk analysis of the thermal sterilization process. Analysis of factors affecting the thermal resistance of microorganisms

A risk analysis was applied to experimental heat resistance data. This anal ysis is an approach for processing experimental thermo-bacteriological data in order to study the variability of D and z values of target microorganis ms depending on the deviations range of environmental factors, to determine the critical factors and to specify their critical tolerance. This analysi s is based on sets of sensitivity functions applied to a specific case of e xperimental data related to the thermoresistance of Clostridium sporogenes and Bacillus stearothermophilus spores. The effect of the following factors was analyzed: the type of target microorganism; nature of the heating subs trate; pH, temperature; type of acid employed and NaCl concentration. The t ype of target microorganism to be inactivated, the nature of the substrate (reference or real food) and the heating temperature were identified as cri tical factors, determining about 90% of the alteration of the microbiologic al risk. The effect of the type of acid used for the acidification of produ cts and the concentration of NaCl can be assumed to be negligible factors f or the purposes of engineering calculations. The critical non-uniformity in temperature during thermobacteriological studies was set as 0.5% and the c ritical tolerances of pH value and NaCl concentration were 5%. These result s are related to a specific case study, for that reason their direct genera lization is not correct. (C) 1999 Elsevier Science B.V. All rights reserved .