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Caution when using dried mushrooms!
06/2002, 28.02.2002
BgVV observes increased incidence of Salmonella
The National Reference Laboratory for Salmonella (NRL-Salm) within BgVV is receiving more Salmonella isolates from dried mushrooms from the German Laender. Since 1998 the number has been steadily increasing. In the first two months of this year alone, the Reference Laboratory received 48 isolates of this kind. A particularly high number of dried mushrooms contaminated with Salmonella was found in south-west Germany. But in other regions of Germany, too, the number of dry mushroom samples with microbial contamination increased last year. The samples were taken from mushrooms imported from Asia. The isolated pathogens belonged to different types of Salmonella. This indicates that this is not a problem pertaining to one batch but rather a general hygiene problem.
If the mushrooms contaminated with Salmonella are prepared according to the instructions, then no acute health risk is to be expected from the prepared food. Correct preparation means heating them to 80°C for at least ten minutes. This temperature and the length of cooking kill the pathogens. However, whilst soaking the mushrooms the Salmonella may multiply to a considerable degree on the soaking mushrooms - particularly if this is done overnight in lukewarm water. When combined with water and heat the mushrooms are a suitable culture medium for the pathogens. When preparing the mushrooms in the kitchen, there is always the possibility of a cross-contamination, i.e. the migration of pathogens from one food to another which previously had not been contaminated with Salmonella. This includes salad or sprouts which are frequently eaten raw. But contamination of desserts and other products, which are not heated prior to consumption, is also conceivable.
It is, therefore, particularly important when preparing dried mushrooms to pay attention to hygiene in the kitchen. The same rules apply as to the preparation of poultry meat. Salads, sprouts and other foods, which are not going to be cooked, should be prepared separately. Kitchen appliances (containers, chopping boards, cutlery), work tops and hands should be washed if they come into contact with the rehydrated mushrooms. The water in which the mushrooms were soaked should be disposed of to prevent it contaminating other foods.
BgVV is, therefore, calling on the producers and importers of dried mushrooms to remove the causes of contamination with Salmonella and to ensure that only hygienically safe products reach the consumer.