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Expressing the equivalence of non‐isothermal and isothermal heat sterilization processes
Author(s) -
Corradini Maria G,
Normand Mark D,
Peleg Micha
Publication year - 2006
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2416
Subject(s) - spore , equivalence (formal languages) , isothermal process , sterility , sterilization (economics) , mathematics , thermodynamics , statistics , chemistry , food science , toxicology , biology , environmental science , botany , physics , discrete mathematics , business , foreign exchange market , finance , exchange rate
Currently, the sterility of heat‐processed food and pharmaceuticals is assessed in terms of an F 0 value, based on the equivalence of the heat treatment to an isothermal process at a reference temperature. This F 0 value, however, has a meaning if, and only if, the inactivation kinetics of the targeted spores (or cells) follow a first‐order relationship and the temperature dependence of the D value, the reciprocal of the rate constant, is log‐linear. There is growing evidence that these conditions are not satisfied by many spores, including those of Clostridium botulinum and vegetative cells. Consequently, a replacement for the F 0 value is proposed in the form of a momentary equivalent time at the reference temperature based on the actual survival pattern of the spores, which need not be log‐linear. This equivalent time can be calculated together with the theoretical survival ratio in real time, thus enabling an operator to monitor the lethality of ongoing industrial heat processes. The concept is demonstrated with published survival data of C. botulinum, for which the Weibullian and log‐logistic models served as primary and secondary models, respectively. The safety factor according to the proposed method is in the number of added minutes of processing, beyond the theoretical time needed to reduce the survival ratio of the targeted spores or cells to a level that would produce practical (or commercial) sterility. Copyright © 2006 Society of Chemical Industry