Staphylococcus aureus Growth and Thermostable Nuclease and Enterotoxin Production in Canned Salmon and Sardines

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Abstract
Staphylococcus aureus growth, thermostable nuclease (TNase) and enterotoxin production in inoculated canned salmon incubated at 22 ± 1°C for 4 d were dependent on the size of inoculum, and on the amount of oxygen present in the headspace; under nitrogen with an inoculum of 7 cfu/can, 102–103 cfu/g, no TNase and traces of enterotoxins (A, B, C2) were observed; under oxygen with the same inoculum ≥109 cfu/g, ≥6.0 μg TNase and up to 5.2 μg total enterotoxins (A, B, and C2)/100 g of salmon were observed. Values were intermediate under atmospheric air. After 1 week, 2 months and 4–24 months of incubation of salmon under nitrogen, S. aureus cfus were 108, 106 and 104–105 per g; TNase ranged from trace amounts to 20 μg/100 g and total enterotoxins from <1.0 μg to 6.2 μg/100 g. In canned sardines stored from 1 d to 12 months at 22 ± 1°C, levels were 109 cfu/g and 3.7–3.9 μg total enterotoxins/100 g; after 1 week, counts declined to 105 cfu/g but total enterotoxins remained relatively stable in some cans with up t...