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BgVV demands lower assessment value for listeria in foods

06/2000, 25.02.2000

The recall of Harz cheese contaminated with listeria in Germany by a food chain and the cases of severe listeriosis disease in France have once again prompted the Federal Institute for Health Protection of Consumers and Veterinary Medicine (BgVV) to call on food manufacturers to ensure through improved hygiene in production that foods are free, if possible, of listeria. The Länder control authorities should pay special attention to these problems. Already one year ago BgVV pointed out that specific foods, including above all raw milk products but also some meat and fish products and foods of plant origin, may be contaminated with listeria.

Listeria are bacteria which are widespread in the environment above all in agriculture. The species Listeria monocytogenes also plays a role as a pathogen in humans and animals. In humans the disease is normally relatively harmless, similar to an influenza infection. Some risk groups, including pregnant women and newborn babies, may develop serious symptoms (stillbirth or pre-term births and infant listeriosis). In older people and people with a weakened immune response to infection, severe forms of listeriosis may occur with the clinical picture of meningitis or sepsis. 30% of these cases are fatal.

Food may become contaminated with listeria at various stages in production and processing. Foods of animal origin in particular like raw milk and raw meat may become contaminated during collection, e.g. during milking or slaughter. Therefore, it cannot be ruled out that in cheeses manufactured from raw milk, contamination of the starting milk is the cause for the occurrence of listeria in the final product. In the case of cheese made from heat treated milk, listeria are normally killed during the correctly carried out pasteurisation of milk. Poor hygiene in the processing stage may open the door to new contamination opportunities for the product after heat treatment. This applies not only to cheese but also to other foods of animal and plant origin. Examples of poor hygiene are dirty working surfaces and appliances in the food plants, poor or too infrequently cleaned slicing machines in the food trade and shortcomings in the personal hygiene of staff.

The ability of listeria to survive and multiply in food depends on the manufacturing methods, further technological treatment and storage conditions. Boiling, roasting, sterilising and pasteurising all kill the bacteria. In foods which contain too little water, too much salt or preservatives or are very acidic (e.g. sauerkraut, mixed pickles and yoghurt), multiplication is delayed or not possible at all. Listeria have good growth opportunities compared to competitive germs where there is a reduced oxygen supply (e.g. in vacuum-packed sausages for heating in simmering water and smoked fish) and long storage times of the food under refrigerated conditions.

For the above reasons it is likely that many foods contain listeria. As a consequence, infections in humans cannot be ruled out according to the current level of scientific knowledge. The infection risk can however be reduced if consumers, in particular people with a weakened immune system,

  • thoroughly cook meat and fish dishes,
  • boil raw milk and
  • do not eat minced meat raw.

In addition, pregnant women should not eat raw milk soft cheese and should not eat cheese rind (of other types of cheese as well).

Furthermore, BgVV recommends strict compliance with the minimum shelf life date in the case of perishable foods and, where possible, consumption of vacuum-packed products long before this date expires.

For milk and dairy products no germs of Listeria monocytogenes may be detected on the manufacturer, wholesale or intermediate levels.

What is more, BgVV recommends lowering the assessment value for listeria in ready-to-eat foods. In future, ready-to-eat foods should already be rejected when they contain more than 100 germs per gram or millilitre food. This value should apply for the duration of consumption within the minimum shelf life. Food producers are called on to guarantee this new, tighter assessment value through corresponding measures and confirm through studies that a multiplication of the pathogens beyond this assessment value is not possible during this period of time.

This BgVV recommendation is currently being co-ordinated with the Länder food control authorities.

Furthermore, BgVV will press for the suggested assessment value to be introduced throughout the European Union in order to improve and harmonise consumer health protection across the EU.


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