Listeria research forces bacteria to jump hurdles

by Editor fleischwirtschaft.com
Wednesday, September 28, 2011
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Greg Jones Europa


A new research project is underway at Campden BRI aimed at using "hurdle technology" to help food firms manufacture products with less susceptibility to listeria.

The microbiologist managing the project at the UKbased food research organisation, Greg Jones, said in a company podcast that the bacteria was a growing problem in Europe. The issue here is that listeria is on the rise. Particularly in Europe, more and more cases of listeria occur.

Manufacturers are under pressure to remove inhibitory compounds from their products such as salt and preservatives in a bid for healthier and clean-label type products, he added.

Jones defined hurdle technology as the application of a series of sub-lethal stresses to a food product, to discover exactly what combinations of sub-lethal stress were inhibitory to listeria microflora.

Previous work has shown that if different stress factors are applied to bacteria, the order in which they are applied will determine the potential for bacterial survival or death during subsequent storage.

Campden BRI's 3-year research programme - now underway for six months with first results expected at the year's end - will examine a range of stresses used in hurdle technology, such as storage temperature, pH, salt, heat, process and preservatives.

Scientists at Campden BRI were using a broth-based system and analysing thousands of broths with different combinations of stresses in them to gather "growth or no-growth data" on listeria from each. Doing so, the researchers can narrow that down and look at the order of the application of the stress, and also at exactly what levels of salt, for example, are going to be sub-lethal in combination with another stress.

Jones explained that the research would also examine "cross-protection", whereby one inhibitory hurdle might potentially protect listeria cells against other stresses. If a sub-lethal stress is applied then sometimes a cross-protection to a second stress happens, sometimes not.

The way to figure that out is to look at a molecule called SigmaB in listeria. If cross-protection is going to happen SigmaB is produced, if it is not then it is not produced.
Jones added, that if the researchers can find out which stresses make this molecule appear, they can predict that cross protection is either likely or unlikely to happen in response to a given sub-lethal stress.
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