Purpose: Our aim was to quantify and model the inactivation of Salmonella in pork burger patties for different internal cooking temperatures and fat levels.
Methods: Pork mince with either a ‘regular’ or reduced fat content was inoculated with one of 3 Salmonella serovars (Salmonella 4,[5],12,i:-, Salmonella Senftenberg and Salmonella Typhimurium) and formed into 144 patties of ~100 g with ~8 cm diameter and ~2 cm thickness. Each patty was then cooked to one of 7 internal endpoint temperatures (45, 48, 51, 54, 57, 60, 63°C), determined by a thermocouple placed at the geometric center of the burger; uncooked patties were retained to estimate the initial concentration of Salmonella. Salmonellae were enumerated in cooked and raw burgers and a generalized linear model (log (Salmonellae) vs fat and endpoint internal temperature) was derived from these data.
Results: The concentration of Salmonella in the raw pork burger patties was 7.47 ± 0.29 log CFU/g. In pork mince with regular fat content (9.2%), the rate of Salmonella inactivation was estimated at -0.254 log CFU/g per 1°C increase above 40°C in end-point temperature, with a ‘five-log’ reduction in Salmonella estimated to occur at a geometric center temperature of 62.7°C. Higher fat content of the mince slightly enhanced Salmonella survival in less ‘done’ burgers although the significance of this observation is not strong (P = 0.056) and the difference is eliminated as the internal temperature approaches 63°C.
Significance: The data and model can be used to inform commercial pork burger cooking process validation and used to support quantitative risk assessments.