Purpose: In this study the microbiological quality of frozen raw shrimp was investigated. The use of 3 intervention technologies to inactivate Listeria on shrimp was also investigated.
Methods: Thirty-two frozen shrimp samples, both imported and domestic, were tested for aerobic plate counts (APC at 22 and 37 °C), coliforms, and Enterbacteriaceae, using USDA Food Safety Inspection Service (FSIS) Microbiological Laboratory Guide procedures, as now FSIS is responsible for testing some aquaculture products. FSIS procedures were also used to determine the incidence of L. monocytogenes (LM), Salmonella spp., S. aureus on the shrimp samples. Three intervention technologies, ultraviolet light (254 nm, 0.5 to 2.0 J/cm2), ozonated water (2 ppm, 0.25 to 2 min.), and gamma radiation (1.0 to 5.0 kGy) were used to inactivate L. innocua, a LM surrogate, surface inoculated onto shrimp in a pilot plant setting.
Results: The average APCs were approximately 4.06 and 3.64 log CFU/g at 22 and 37 °C, while coliforms and enteric bacteria were approximately 0.02 and 1.43 log CFU/g, respectively. None of the samples tested positive for Salmonella spp., S. aureus using the BAX-TM polymerase chain reaction detection. 7/32 tested positive for Listeria spp., and viable LM was recovered from 4 (12.5%) of the 32 shrimp samples. Ultraviolet light (2 J/cm2) inactivated approximately 0.4 log CFU/g, ozonated water (2 ppm, 2 min) inactivated 1.5 log CFU/g, and 5 kGy gamma radiation inactivated > 5 log CFU/g of L. innocua, respectively.
Significance: Additional research is needed to determine the effect of commonly used intervention technologies on the detection and isolation of foodborne pathogens in seafood products.