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Safety evaluation of sous vide-processed ready meals
H Nissen1, J T Rosnes, J Brendehaug
1MATFORSK, Norwegian Food Research Institute, Osloveien 1, N-1430 As, Norway. hilde.nissen@matforsk.no
Aims:
To assess survival, growth and toxin production of spore-forming bacteria in sous vide products exposed to a relatively high heat treatment.
Methods And Results:
During a three-year period, 2,168 sous vide-processed, commercially available ready-made meals with a shelf life of 3-5 weeks were examined. The products were stored at 4 degrees C for the first 1/3 and at 7 degrees C for the remaining 2/3 of their shelf life period. Three-fourths of the samples had less than 10 bacteria per gram the day after production, and none had more than 1,000. Similar numbers were found at the end of the shelf life when stored as described above. At abuse temperature (20 degrees C), the number of bacteria increased to 10(6)-10(7) cfu g(-1) 7 d after production. A total of 350 isolates of Bacillus spp. were collected, but no Clostridium strains were detected. Only 11 of the 113 tested strains were able to grow at 7 degrees C in broth, and none of the psychrotrophic strains were able to produce substantial amounts of toxins causing food poisoning.
Conclusion:
The health risk of these products is small as long as the temperature during storage is low. For microbial testing of the end products, traditional plating will suffice.