Effects of Storage Temperatures on Survival and Enterotoxin Production of Staphylococcus Aureus in Turkish White Pickled Cheese

Abstract

Aims: Turkish white pickled cheese is the most consumed cheese type in Turkey and it is an important food to be evaluated in terms of food safety. In this study we investigated the behavior (survival and production of enterotoxin) of Staphylococcus aureus (S. aureus) NCTC 10654 in Turkish white pickled cheeses, which were ripened at 4 °C and 12 °C for 90 days. Methodology and results: Counting of microorganisms was carried out by conventional methods on appropriate media. Detection of enterotoxins was performed by double-sandwich ELISA technique and gene region responsible for enterotoxin production by reverse transcription-PCR (RT-PCR). The counts of S. aureus decreased (p<0.05) in all of the cheese samples during ripening, where they decreased by 102(CFU/g) at the end of the 90-day ripening period. The reduction in the S. aureus count was 2.5 times lower in cheeses ripened at the higher temperature, but the temperature was determined that had no significant effect on S. aureus survival (p >0.05). Staphylococcal enterotoxin could not be detected in the cheeses during ripening. Staphylococcal enterotoxin (SE) B mRNA was detected in cheese samples on days 1, 15, and 30 of ripening by RT-PCR. The SEB mRNA expression levels had differed according to the storage temperature. Conclusion, significance and impact of study: This study showed that enterotoxin B producing S. aureus decreased in Turkish white pickled cheese stored at different temperatures and it could not produce enterotoxins, possibly due to factors such as type and nature of the cheese, and the conditions of production and activity of the starter culture.