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J. N. LIU, J. P. Smith, I. Tarte, and C. Simard. Department of Food Science and Agricultural Chemistry, McGill University, 21,111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada

JUSTIFICATION: Concerns has been expressed about the public health safety of modified atmosphere packaged (MAP) foods, specifically with respect to the growth of psychrotrophic pathogenic microorganisms, such as Listeria monocytogenes. L. monocytogenes is a major problem since it can be found in seafood products and it may grow in high level of CO₂ packaging condition commonly used in MAP. It is very important to address this issue in the newly developed MAP value-added trout products at refrigeration and mild temperature abuse conditions to ensure the safety of the products.

OBJECTIVES: The objectives of this study were to monitor the physical, chemical, microbiological and sensory changes in inoculated studies with L. monocytogenes in value-added trout products (burgers and wontons) packaged under various atmospheres at refrigeration and mild temperature abuse conditions.

METHODS: Value-added trout burgers and wontons were inoculated with 10² CFU/g of L. monocytogenes. All products were packaged under air, air and oxygen absorbent (Ageless SS), and 2 gas packaging conditions (60% and 80% CO₂ , balance N₂). Products were stored at 4 and 12^oC for 28 days. Growth of L. monocytogenes was enumerated by using PALCAM agar supplemented with Palcam Selective Supplement (SR150E).

RESULTS: The results showed that the formulated value-added trout products would support the growth of L. monocytogenes if contaminated. Gas packaging atmosphere of 80% CO₂ (balance N₂) was the only storage condition where no growth was observed in products stored at 4^oC. At 12^oC, counts of L. monocytogenes increased in every products after storage, regardless of packaging atmospheres.

SIGNIFICANCE: These results suggest that there is a potential health risk associated with MAP value-added trout products if contaminated with L. monocytogenes. At mild temperature abuse conditions, the effect of MAP was significantly reduced since L. monocytogenes grew in all atmospheres.