In 2017 in Europe there were 343 reported cases of outbreaks caused by enterotoxins of Staphylococcus aureus. To reduce this risk as far as possible, the European legislation stipulates that cheese must be examined for coagulase-positive staphylococci (CPS) when the amount of cells is supposed to be highest. If at this point CPS counts exceed 105 CFU/mL, the cheese must be examined for the presence of enterotoxins and, if positive, destroyed. Manufacturers of Swiss alpine cheese were exempt from this obligation because enterotoxin formation in hard cheese was expected to be very unlikely given the high scalding temperatures leading to early inactivation of CPS in the curd. However, this assumption has not yet been scientifically proven. Therefore, a laboratory-scale cheese production was developed which corresponds to practical conditions regarding time course of temperature and cheese composition. Raw milk aliquots (200 mL) were inoculated with five different strains of CPS and processed to cheese applying scalding temperatures ranging from 46 – 56 °C. The temperature control after pressing the curd aimed at reproducing the temperature curve in the peripheral zone of a real cheese wheel. Contrary to the expectations, results showed that the enterotoxin formation was partly possible even at high scalding temperatures (54 - 56 °C), with the differences between the strains being greater than between temperatures. Based on these results, the mechanism of enterotoxin formation in cheese needs to be further studied.
