51A-33

I. DUFRESNE¹, J. P. Smith¹, J. N. Liu¹, J. W. Austin², and B. Blanchfield². (1) Department of Food Science and Agricultural Chemistry, McGill University, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada, (2) Bureau of Microbial Hazards, Health Protection Branch, Health Canada, Banting Building, Tunney's Pasture, Ottawa, ON H9X 3V9, Canada

JUSTIFICATION: Nowadays, smoked fish is processed using less smoke and salt and more moisture compared to the traditional smoking methods, thus providing an ideal substrate for the growth of Clostridium botulinum type E. Since they are minimally processed, smoked products are regarded as hazardous if contaminated with C. botulinum. However, little work has been done to demonstrate botulinal toxin production in smoked fish.

OBJECTIVES: The objectives of this study were to monitor the physical, chemical, microbiological and sensorial changes in inoculated studies with C. botulinum type E in vacuum packaged cold and hot smoked trout fillets with films of different oxygen transmission rates (OTRs).

METHODS: Challenge studies were performed on smoked rainbow trout fillets (~100g) inoculated with 10² spores/g of C. botulinum type E. All products were vacuum packaged in films of different OTRs (12 cc/m²/day/atm @ 24^oC, 0% RH < OTR < 10 043 cc/m²/day/atm @ 24^oC, 0% RH) and stored at 4, 8 and 12° C for 28 days. Mouse toxicity test was used for toxin detection. Samples were considered positive for toxin if 2/2 or ³ 2/4 mice died.

RESULTS: While no sample was toxic at 4^oC, 50% of the cold smoked trout fillets and 75% of the hot smoked fillets were toxic at 8^oC. All products were toxic after 28 days at 12^oC, irrespective of film OTRs. In some cases, spoilage preceded toxigenesis, while in others, toxigenesis preceded spoilage.

SIGNIFICANCE: This study indicates that if smoked fish are contaminated by C. botulinum type E they may pose a public health risk since these are ready-to-eat foods. At 4^oC, temperature is more important than film OTR to control toxin production by C. botulinum type E. However, at mild temperature abuse conditions, packaging films' OTR cannot be regarded as a safety barrier for smoked trout fillets.