Behavior of Salmonella and Listeria monocytogenes in Raw Yellowfin Tuna during Cold Storage

Abstract

Behavior of <i>Salmonella</i> and <i>Listeria monocytogenes</i> in raw yellowfin tuna during refrigeration and frozen storage were studied. Growth of <i>Salmonella</i> was inhibited in tuna during refrigerated storage, while <i>L. monocytogenes</i> was able to multiply significantly during refrigerated storage. Populations of <i>Salmonella</i> in tuna were reduced by 1 to 2 log after 12 days of storage at 5-7 °C, regardless levels of contamination. However, populations of <i>L. monocytogenes</i> Scott A, M0507, and SFL0404 in inoculated tuna (10⁴-10⁵ CFU/g) increased by 3.31, 3.56, and 3.98 log CFU/g, respectively, after 12 days of storage at 5-7 °C. Similar increases of <i>L. monocytogenes</i> cells were observed in tuna meat with a lower inoculation level (10²-10³ CFU/g). Populations of <i>Salmonella</i> and <i>L. monocytogenes</i> declined gradually in tuna samples over 84 days (12 weeks) of frozen storage at -18 °C with <i>Salmonella</i> Newport 6962 being decreased to undetectable level (<10 CFU/g) from an initial level of 10³ log CFU/g after 42 days of frozen storage. These results demonstrate that tuna meat intended for raw consumption must be handled properly from farm to table to reduce the risks of foodborne illness caused by <i>Salmonella</i> and <i>L. monocytogenes</i>.