title: Effects of frozen storage on survival of Staphylococcus aureus and enterotoxin production in precooked tuna meat.
abstract: This study investigated the survival of Staphylococcus aureus in precooked tuna meat for producing canned products during frozen storage (-20 ± 2 °C) as well as its growth and enterotoxin production at 35 to 37 °C after the storage. Samples (50 ± 5 g) of precooked albacore (loin, chunk, and flake) and skipjack (chunk and flake) tuna were inoculated with 5 enterotoxin-producing strains of S. aureus at a level of approximately 3.5 log CFU/g and individually packed in a vacuum bag after 3 h incubation at 35 to 37 °C. Vacuum-packed samples were stored in a freezer (-20 ± 2 °C) for 4 wk. The frozen samples were then thawed in 37 °C circulating water for 2 h and incubated at 35 to 37 °C for 22 h. Populations of S. aureus in all precooked tuna samples decreased slightly (<0.7 log CFU/g) after 4 wk of storage at -20 ± 2 °C, but increased rapidly once the samples were thawed and held at 35 to 37 °C. Total S. aureus counts in albacore and skipjack samples increased by greater than 3 log CFU/g after 6 and 8 h of exposure to 35 to 37 °C, respectively. All samples became spoiled after 10 h of exposure to 35 to 37 °C, while no enterotoxin was detected in any samples. However, enterotoxins were detected in albacore loin and other samples after 12 and 24 h of incubation at 35 to 37 °C, respectively. Frozen precooked tuna meat should be used for producing canned tuna within 6 to 8 h of thawing to avoid product spoilage and potential enterotoxin production by S. aureus in contaminated precooked tuna meat.
authors.affiliation: Seafood Research and Education Center, Oregon State Univ, 2001 Marine Drive, Room 253, Astoria, OR, 97103, U.S.A.
authors.forename: Xulei
authors.initials: X
authors.lastname: Wu
authors.forename: Yi-Cheng
authors.initials: YC
authors.lastname: Su
mesh_terms: D000818:Animals; D015169:Colony Count, Microbial; D004768:Enterotoxins / Q000096:biosynthesis*; D005506:Food Contamination / Q000517:prevention & control; D005516:Food Microbiology; D061353:Food Storage / Q000379:methods*; D005615:Freezing; D017747:Seafood / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000254:growth & development / Q000302:isolation & purification*; D014413:Tuna / Q000382:microbiology*
chemical_list: D004768:Enterotoxins
keywords: Staphylococcus aureus; enterotoxin; food safety; precooked tuna; seafood