Effect of Temperature on the Production of Staphylococcal Enterotoxin and Thermal Inactivation Kinetics of Staphylococcus aureus in Selected Ready-to-Eat (RTE) Foods in Korea

This study quantitatively analyzed staphylococcal enterotoxins (SEs) produced by Staphylococcus aureus in contaminated ready-to-eat kimbabs and sandwiches stored at 17 to 30C. To detect a TECRA SE, visual immunoassay kit and an enzyme-linked immunosorbent assay reader was used. The amount of SE in the kimbab was positively correlated with the growth of S. aureus at all storage temperatures except for 17C. The maximum amount of SE in the sandwich did not exceed 0.5 ng/g, regardless of storage temperature. The maximum amounts of SE in the kimbabs and sandwiches were 1.8 ng/g and 0.15 ng/g after 30.5 and 52 h at 30C, respectively, indicating that SE production was dependent on the types of food matrix. In addition, the thermal inactivation of staphylococcal enterotoxin D (SED) producing S. aureus in the kimbabs and broth was determined at temperatures 51 to 63C, and the D- and z-values were calculated. Significant differences in the D-values between the kimbab and broth were observed at 51 to 63C, but the z-value was not significantly affected by the model medium. Practical Application Staphylococcal enterotoxin production is dependent on the types of food matrix and storage temperature, regardless of the growth of S. aureus in food. Thermal inactivation kinetics of S. aureus, which was obtained in this study, can be used in designing thermal times and temperatures of ready-to-eat food during heat processing.