Enhanced Thermal Resistance of Salmonella in Whole Muscle Compared to Ground Beef

Irradiated beef (whole -muscle and ground product with identical fat, protein, and moisture composition) was exposed to a Salmonella- inoculated marinade and heated in brass tubes in a water bath at 55 °C, 60 °C, and 62.5 °C. The bacterial load and thermal lag time were similar ((alpha) = 0.05) for both whole and ground muscle; therefore, all samples had equivalent composition, inoculation levels, and thermal histories. Assuming 1st-order kinetics, the inactivation rate constants (k values) in whole muscle were 50% lower than those in ground product at each temperature (P = 0.0001), and Arrhenius-type models described the temperature dependency of k (R^2> 0.95). Because thermal processing regulations are generally based on ground product studies, thermal process validations for meat and poultry products may need to consider the physical state (whole -muscle versus ground) of the product being manufactured.