Purpose: The object of this study was to investigate the effect of temperature on the possibility of Staphylococcus aureus (ATCC 13565) growth and enterotoxin A (SEA) production on beef jerky with low water activity at retail markets.
Methods: Beef jerky without seasoning was purchased and inoculated with S. aureus producing enterotoxin A at a concentration of approximately 3-4 log CFU/g. The Gompertz model was used to obtain growth kinetics and the concentration of SEA was measured using a RIDASCREENSET Total Kit (R-biopharm, Darmstadt, Germany) at 19, 20, 21, 25, 30, and 35°C.
Results: The growth of S. aureus on beef jerky was observed at 21°C. As the temperature increased (21, 25, 30 and 35°C), the LT values decreased from 31.73 to 16.35 h, and the SGR and MPD values increased from 0.012 to 0.120 log CFU/g/h and from 4.9 to 7.5 log CFU/g, respectively. At 25 and 30°C, SEA was not produced on beef jerky, but the concentration of SEA reached 0.24 ng/ml (7.5 log CFU/g) after 77 h storage at 35°C.
Significance: Despite the low water activity (Aw) of beef jerky (0.754), the growth of S. aureus and SEA production was observed at 21°C and at 35°C, respectively. Thus, beef jerky must be stored temperature lower than 21°C at the market and home to prevent risk of foodborne illness due to S. aureus growth.