Structural model requirements to describe microbial inactivation during a mild heat treatment

The classical concept of D and z values, established for sterilisation proc esses, is unable to deal with the typical non-loglinear behaviour of surviv or curves occurring during the mild heat treatment of sous vide or cook-chi ll food products. Structural model requirements are formulated, eliminating immediately some candidate model types. Promising modelling approaches are thoroughly analysed and, if applicable, adapted to the specific needs: two models developed by Casolari (1988), the inactivation model of Sapru ct al . (1992), the model of Whiting (1993), the Baranyi and Roberts growth model (1994), the model of Chiruta et al. (1997), the model of Daughtry et al. ( 1997) and the model of Xiong et al. (1999). A range of experimental data of Bacillus cereus, Yersinia enterocolitica, Escherichia coli O157:H7, Lister ia monocytogenes and Lactobacillus sake are used to illustrate the differen t models' performances. Moreover, a novel modelling approach is developed, fulfilling all formulated structural model requirements, and based on a car eful analysis of literature knowledge of the shoulder and tailing phenomeno n. Although a thorough insight in the occurrence of shoulders and tails is still lacking from a biochemical point of view, this newly developed model incorporates the possibility of a straightforward interpretation within thi s framework. (C) 2000 Elsevier Science B,V. All rights reserved.