Purpose: The object of this study was to evaluate survival of S. aureus and production of Staphylococcal enterotoxin A on dried filefishes and julienned squid at 10, 24, and 35°C.
Methods: Dried filefishes and julienned squid were inoculated with enterotoxin A producing S. aureus at a concentration of 106CFU/g, respectively, and packed into polyethylene bags for storage at 10, 24 and 35°C. At selected times after inoculation, the diluted samples were plated onto Baird-Parker agar in duplicate, and incubated at 35°C for 48 h. Production of Staphylococcal enterotoxin A in dried fishery products was analyzed using a TECRA SE visual immunoassay kit and ELISA reader.
Results: S. aureus on both dried filefishes and julienned squid survived longer at 10 °C than 24 or 35°C. After 5 months storage, populations of S. aureus resulted in reduction of 1~1.7 at 10 °C and 5~5.5 log CFU/g at 24°C. At 35°C, S. aureus was undetectable on dried filefishes and julienned squid after 14 and 16 days, respectively. Toxin production was not increased during 5 months, regardless of storage temperature. Survival kinetic parameters of the observed data were also well fit to the Weibull equation (GIna FiT v1.5, R2>0.95). Shape(P) and scale(delta) values of the Weibull equations were further described in a secondary model as a function of temperature using second-order polynomial model.
Significance: The quality of dried fishery products was better maintained at 10°C. However, the low storage temperature has more potential for S. aureus survival on dried fishery products than ambient temperatures and thus causes a potential safety risk of the dried fishery products.