Last updated on 6 March 2013
Safety of sous vide foods: Feasibility of extending ComBase to describe the growth/survival/death response bacterial foodborne pathogens between 40º and 60ºC.
A new generation of foods (often called sous vide foods) are being developed that are cooked at low temperatures. There is a gap in data for models for food pathogens at these temperatures. The project informed the FSA on this issue and proposed a way forward to fill the knowledge gap.
Study duration: February 2012 to May 2012
Contractor: Institute of Food Research Enterprises
Project code: FS246004D/FS102028
Traditionally food has been cooked at high temperatures. Sous vide is a method of cooking food vacuum packed in a sealed plastic pouch, then cooked by submersion in a water bath. Recent years have seen an increase in the number of sous vide foods being cooked at low temperatures (e.g. 42°C to 70°C).
At present growth models for vegetative pathogens go to about 40°C while thermal death models are from about 55 to 60°C upwards. There is a lack of information in the range of about 40 to 60°C . This makes it difficult to assess the safety of these new sous vide foods that are cooked in a water-bath at around 50 to 70 °C.
This work involved a feasibility study on extending models in the database called 'Combase Predictor' . It allowed the calculation of the lethal effect, normally associated with heat treatments at relatively low temperatures, on the reduction of food pathogens.
The work gathered information that could be used to assess the hazard associated with lower temperature cooking. It also investigated how much work is needed to upgrade the database used to model the hazards. This helped ensure that the safety assessment for such sous vide foods is consistent, effective and commensurate with any risk to public health.
ComBase (www.combase.cc) is the primary web-based resource for quantitative and predictive food microbiology. A study was carried out on the feasibility of extending ComBase models to describe the behaviour of E. coli, salmonella and L. monocytogenes between around 40 and 60°C .
This involved assessing the extent and quality of current data, analysis of current data and identification of how much additional data would be required to generate a robust thermal death model for these pathogens. The modelling techniques required to extend the death models in ComBase were assessed and the amount of additional data and work to extend models for ComBase Predictor was identified.
Results and findings
The project explored the feasibility of extending models, such as those in ComBase, to cover low temperature heat treatments. The aim was to help assess pathogen survival, which may contribute to providing improved assessment of sous vide safety.
- gathered data on the use of sub 60°C cooking processes
- gathered and assessed the quantity and quality of the available data on the kinetics of bacterial populations between 40°C and 60°C
- assessed the feasibility of extending growth and thermal death models for E.coli, salmonella and L. monocytogenes
The main findings were as follows:
- The most common uses of sub 60°C cooking temperatures were for steaks, fish and seafood
- The collected data clearly showed that the majority of kinetic thermal death data has been collected at 55°C and above and there was limited kinetic data on growth at temperatures above 40°C. The data found was not sufficient to create a model that would cover the entire 40°C to 60°C range
- There are many types of models that could be created to compare the behaviour of bacteria in sous vide systems to that in conventional foods. These vary in the work needed to create them, complexity of use and the quantity of new information that would have to be acquired
- Some of the existing data could be used for validation if any model created was general rather than for specific food types. The types of models that could be envisaged are described in the report. The use of models to aid the safe production of foods using the sous vide cooking method was also discussed