Thermal Inactivation of the Heat-Resistant Pathogens Salmonella Senftenberg 775W and Escherichia coli AW1.7 in Whey Concentrate

Pasteurized whey concentrate is used as a base for the production of ingredients for various food products. Whey concentrate (30% dry matter) was used to assess the thermal inactivation of Salmonella (S.) enterica serovar Senftenberg 775W (DSM 10062) and Escherichia (E.) coli AW1.7 (DSM 108612) strains in a pilot-scale pasteurizer mimicking industrial heat processing. These strains, chosen for their exceptional heat resistance, represent the most challenging scenario for pasteurization within the context of S. enterica and E. coli. Heat resistance was tested at temperatures of 56, 60, 64, 68, and 72 °C at an average holding time of 17.5 s. These exceptionally heat-resistant strains showed a relatively low reduction in numbers of between 0 and 4.2 log10 CFU/mL at lower inactivation temperatures of ≤68 °C. A reduction of at least 5 log10 CFU/mL, as required for adequate heat processing, was achieved for both species after heating at 72 °C for 17.5 s. This study shows that whey concentrate should not lead to contamination of food ingredients and can be considered safe after pasteurization at 72 °C for at least 17.5 s with respect to the pathogens tested.