Modeling the Process and Formulation Conditions That Prevent the Outgrowth of Non-proteolytic Clostridium botulinum in Chilled Foods.

The European ready meals market is growing, with increased demand for convenient, minimally processed foods. Refrigerated processed foods of extended durability (REPFEDs) rely on mild heat treatments and chilled storage, which may allow survival of non-proteolytic Clostridium botulinum, a pathogen capable of producing botulinum neurotoxin at low temperatures. The objective of this study was to investigate combinations of mild heat-treatment conditions (below 90 °C for 10 min) and mild acidic conditions (pH above 5), which may prevent the outgrowth, namely the inhibition, of non-proteolytic Clostridium botulinum in chilled foods. This study used a probabilistic model integrating literature data, previous predictive models, realistic domestic storage conditions of chilled temperatures, and time of consumption. The model was implemented in the R software with variability and uncertainty separated. Results indicated that a heat treatment of 85 °C for 18  min led to a time before outgrowth of 104 days (95% uncertainty interval: 76-156 days). In this specific process and formulation condition, the probability of inhibition for a product having a Use-by-Date of 28 days was estimated at 0.06% (95% uncertainty interval 0.00-0.4%). That corresponded to a level of inhibition of 3.2 log (1/0.0006) CFU/g. Similarly, a heat-treatment of 84 °C for 10 min combined with a pH of 6.4, or a heat-treatment of 87 °C for 10 min at pH 6.6, enabled to reaching 3 log CFU/g of spore outgrowth inhibition. These findings help to design safe REPFEDs under mild thermal treatment and pH, considering realistic domestic storage conditions. The study also illustrates the added value of modeling approach to capitalize on existing literature information.