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Applied and Environmental Microbiology, January 2000, p. 223-229, Vol. 66, No. 1
0099-2240/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Safety Evaluation of Sous Vide-Processed Products with Respect to Nonproteolytic Clostridium botulinum by Use of Challenge Studies and Predictive Microbiological Models

Eija Hyytiä-Trees,1,* Eija Skyttä,2 Mirja Mokkila,2 Arvo Kinnunen,2 Miia Lindström,1 Liisa Lähteenmäki,2 Raija Ahvenainen,2 and Hannu Korkeala1

Faculty of Veterinary Medicine, Department of Food and Environmental Hygiene, University of Helsinki, Helsinki,1 and VTT Biotechnology and Food Research, Espoo,2 Finland

Received 21 June 1999/Accepted 2 November 1999

Sixteen different types of sous vide-processed products were evaluated for safety with respect to nonproteolytic group II Clostridium botulinum by using challenge tests with low (2.0-log-CFU/kg) and high (5.3-log-CFU/kg) inocula and two currently available predictive microbiological models, Food MicroModel (FMM) and Pathogen Modeling Program (PMP). After thermal processing, the products were stored at 4 and 8°C and examined for the presence of botulinal spores and neurotoxin on the sell-by date and 7 days after the sell-by date. Most of the thermal processes were found to be inadequate for eliminating spores, even in low-inoculum samples. Only 2 of the 16 products were found to be negative for botulinal spores and neurotoxin at both sampling times. Two products at the high inoculum level showed toxigenesis during storage at 8°C, one of them at the sell-by date. The predictions generated by both the FMM thermal death model and the FMM and PMP growth models were found to be inconsistent with the observed results in a majority of the challenges. The inaccurate predictions were caused by the limited number and range of the controlling factors in the models. Based on this study, it was concluded that the safety of sous vide products needs to be carefully evaluated product by product. Time-temperature combinations used in thermal treatments should be reevaluated to increase the efficiency of processing, and the use of additional antibotulinal hurdles, such as biopreservatives, should be assessed.


* Corresponding author. Mailing address: 1409 Millstream Trail, Lawrenceville, GA 30044. Phone: (678) 380-9923. Fax: (404) 639-3333. E-mail: eih9{at}cdc.gov.


Applied and Environmental Microbiology, January 2000, p. 223-229, Vol. 66, No. 1
0099-2240/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.