A vitalistic approach for non-thermal inactivation of pathogens in traditional Greek salads

Abstract

A vitalistic model was developed for the effects of low pH, chill temperatures and oregano essential oil on Salmonella enterica subsp. enterica serotype Enteritidis PT4 (S. Enteritidis PT 4) and Escherichia coli O157:H7 NCTC 12900 in taramasalad and aubergine salad, respectively. The model was based on the concept of the existence of heterogeneous response to stress within a genetically identical bacterial population that is exposed to stress at lethal levels. The imposed stress conditions were mathematically expressed as an argument of a cumulative normal distribution function, to predict the proportion of survivors at a given time of exposure. For each food, the modelling procedure consisted of estimating parameters using nonlinear least squares in one step, resulting in a single equation. The graphical illustration of the fitted model and data confirmed a good fit. Moreover, model comparisons with literature data and Pathogen Modelling Program were carried out to underline the importance and specificity of developing predictive models for survival if pathogens in situ.