Simulating bacteria in food
Experiments involving the simulation of Listeria bacteria lead to safer ready-made food products.
In recent years a host of dishes known as ready-to-eat (RTE) products have been developed. This means that these products do not necessarily require an extra heating process before they are eaten so it is particularly important that they do not contain pathogenic bacteria. In order to ensure that the food products are safe from a health perspective before they are dispatched to the market, they must undergo a documented heat treatment. There are many such treatments and this may for instance be microwave heating or grilling or frying processes that involve several steps. The treatments can provide uneven heating in some products and the production lines must be adjusted to ensure optimal quality and to safeguard that the bacteria are killed.
Secure killing of Listeria
In order to document that the products have received adequate heat treatment and are therefore safe for the consumer, Research Fellow Sonja Grönqvist has worked on two methods of how the pathogenic bacteria Listeria monocytogenes in food may be killed. In one part of the project, Listeria is encapsulated in porous alginate beads (gelatinous beads), which may simulate the structure of the food during heat treatment. The other part of the project utilizes an enzyme that has the same rate of degradation in heat processes as Listeria, and is referred to as a time temperature integrator (TTI). It is easier to use a harmless enzyme when conducting research in real production lines, as this avoids contamination of the processing equipment and foods. This method was tested in full-scale production of grilled fish cakes, and showed that this type of TTI was simple to use and is useful in documenting that secure targets are achieved for heat treatment in complicated heat processes.
Research Fellow Sonja Grönqvist is presenting her thesis for the degree of Licentiate of engineering on this topic on Friday January 17 at Chalmers University of Technology, where she has also taken part of the programme. The title of her thesis is “Validation of mild cooking processes with target of Listeria monocytogenes inactivation to ensure food safety”. External supervision has been provided through the Swedish Institute for Food and Biotechnology (SIK) in Gothenburg, while the practical work has been implemented at Nofima in Stavanger.