Time Temperature Pathogen Predictor (T2P2): Expansion of a Risk Assessment Tool Based on Interval Accumulation of Dynamic Temperature Profiles Associated with Short-term Temperature Abuse of Raw Shrimp

Introduction:   Pathogenic bacterial growth and toxin formation on shrimp can result from short-term temperature abuse and subsequently cause illness from consuming raw, undercooked or re-contaminated shrimp. Pathogens can be introduced during harvest, handling, or processing and further growth can occur during storage and transportation.  Information related to short-term temperature abuse of Vibrio parahaemolyticus (VP), Salmonella sp. (SAL), and Staphylococcus aureus(SA) is needed to mitigate the risks associated with these hazards and to support process deviation decision making.

Purpose:   The purpose of this study is to evaluate the lag phase duration (LPD) and the growth rate (GR,) of VP, SAL and SA at a variety of times and temperatures during short-term temperature abuse in a “real” food matrix and thereby expand the database of the T2P2 predictive modeling tool.     

Methods:   Three separate cocktails (five strains each) of VP, SAL and SA were prepared and inoculated separately into ground shrimp.  The final concentration was approximately 10⁴/g in 25.0 g of shrimp.  The experimental temperature range was 10 – 43.3°C at 10°C increments. Samples were withdrawn at various time intervals at each incremental temperature, diluted and plated on appropriate media and incubated.  Data obtained as CFU/ml were fitted with the DMFit 2.0 program which generated LPD and GR values.

Results:   For all organisms, LPD decreased and GR increased as the temperature increased from 15.6 – 43.3°C.  For example, the LPD for VP decreased ~ 12 fold, from 565 to 46 min, and the GR increased ~ 6 fold,  from 0.004 to 0.023 {log (CFU/ml/min}.  The comparative difference in GR of VP, SAL, and SA at 43.3°C was 0.023, 0.015 and 0.015 {log (CFU/ml/min}, respectively. 

Significance:   The database expansion for shrimp is nearly completed and validation studies are in progress, as is work with Risk Sciences International (software developer) to further develop the T2P2 web-portal and User Guide to aid in the food safety risk decision making process.