The Department for Seafood Research at DIFRES has recently held a successful seminar on the control of Listeria monocytogenes in the seafood industry.
It proved to be a very timely event, given the entry into force on 1st January 2006 of new EU legislation concerning Listeria monocytogenes.
There were about 50 participants: processors, suppliers, participants from administration and consulting groups as well as research and education institutes. The processors were mainly from the fish industry, but other kinds of food industries were also there.
The seminar presented results from a two-year project which has been carried out jointly by the Department of Seafood Research, the consulting group Højmarklaboratoriet and five Danish fish slaughter houses and fish smokehouses.
The overall aim of this project has been to ensure that the level of the pathogenic bacteria Listeria monocytogenes is so low in Danish ready-to-eat (RTE) fish products that they do not constitute a risk to the consumer.
The project has shown that although L. monocytogenes is common in the natural environment, it only appears sporadically outside processing environments (slaughter and smokehouses) and the L. monocytogenes seem to be other sub-types than the L. monocytogenes found inside the processing environments. So it is important to focus on cleaning, disinfection and a dry processing environment to prevent the bacterium from colonizing processing environments.
The project has developed tools and programs for surveillance of the processing environments. The cold-smoking process contains a light salting and smoking at 22-28 ºC. These levels of NaCl and temperature are not in themselves harmful to L. monocytogenes and it has been discussed whether the bacterium may even grow during this process.
This project has shown that the cold-smoking process reduces the level of L. monocytogenes, so it is important to put focus on hygiene in the processing activities after the smoking step so as to avoid transfer of the bacterium to the products. It has also been shown that addition of lactate and diacetate to cold-smoked salmon can inhibit the growth of L. monocytogenes during storage at refrigeration temperatures. These acids can be added to the brine and have no influence on the sensory properties of the product. Low levels of the bacterium only very seldom constitute a risk to the consumer and a major control option is therefore to prevent the bacterium from growing in the product.
A mini poster-session was also held for companies to present their products or techniques that can be used to control L. monocytogenes and other microorganisms. The companies were: Force Technology (SonoSteam), FOODDES, Kemi Service A/S and Brenntag Nordic A/S.
More information can be obtained from Research assistant Cisse Hedegaard Hansen