Staphylococcus aureus Burden in Frozen, Precooked Tuna Loins and Growth Behavior During Typical and “Worst-case” Processing Conditions

FDA's Seafood HACCP Guidance (SHG) recommends a cumulative exposure time limit of 3 h if product temperature exceeds 21.1 °C (70°F) to minimize the growth of Staphylococcus aureus (SA) and prevent staphylococcal enterotoxin (SE) production. This time limit is insufficient to practically accomplish postthawing activities (e.g., packing, brining, sealing, retort staging, and time for the center of the can to reach the critical temperature of 50 °C (122°F)). The documented evidence supporting the establishment of this exposure time recommendation is minimal and mostly irrelevant to tuna. The goal of this study was to provide "real world" and "worst-case" industrial data to support the development of an accurate maximum cumulative exposure time for tuna processing facilities. A total of 48,933 certificates of analysis (COAs) were compiled and reviewed to determine SA detection frequency (2.14%) and estimate quantitative microbial burden. Review of quantitative results indicates the need for careful review and communication with suppliers to correct for dilution factors in analytical methods. SA levels were closely monitored during typical processing conditions on nine production days which demonstrated consistent control of SA populations (<2 log CFU/g increase) between thawing and retort staging. The processing system was challenged on three production days to create "worst-case" processing conditions where open or sealed cans were packed and held for up to 5 h in the retort staging area at 26 °C (78.8°F). Extended holding times of tuna in open cans led to significant increases in SA populations which confirmed the predicted SE production risk for products with high oxygen availability used to develop the SHG guidance. However, extended holding times in sealed cans demonstrated significantly reduced SA growth. This collective and contextual data analysis supports the relaxation of the maximum cumulative exposure time beyond the 3 h recommendation in the SHG.