Thermal inactivation of Escherichia coli O157:H7, Salmonella senftenberg, and enzymes with potential as time-temperature indicators in ground turkey thigh meat.

The USDA Food Safety and Inspection Service has proposed to amend cooking regulations to require that any thermal process used for poultry products be sufficient to cause a 7 D reduction in salmonellae. Several enzymes have been suggested as potential indicators of heat processing in poultry, yet no relationship between the inactivation rates of these enzymes and salmonellae had been determine. The thermal inactivation kinetics of endogenous muscle proteins. Escherichia coli O157:H7 and Salmonella senftenberg were compared in ground turkey thigh meat in thermal death time studies. Bacteria counts were determined and muscle extracts were assayed for residual enzyme activity or protein concentration D and zeta values were calculated using regression analysis. S. senftenberg had higher D values at all temperatures and was more heat resistant than E. coli. The zeta values of E. coli on Petrifilm Coliform Count plates and phenol red sorbitol agar plates were 6.0 and 5.7 degrees C, respectively. The zeta values of S. senftenberg were 5.6 and 5.4 degrees C on Petrifilm and agar, respectively. Lactate dehydrogenase (LDH) was the most heat stable protein at 64 degrees C. LDH, glyceraldehyde-3-phosphate dehydrogenase, creatine kinase, triose phosphate isomerase (TPI), acid phosphatase, serum albumin, and immunoglobulin G had zeta values of 3.8,4.3,4.8,5.8,6.3,6.7, and 8.6 degrees C, respectively , in turkey containing 4.3% fat. The zeta values for TPI decreased to 5.4 degrees C in thigh meat containing 9.8% fat. Temperature function of TPI was most similar to that of S. senftenberg, suggesting it might function as an endogenous time-temperature integrator to monitor adequacy of processing when a performance standard based on this pathogen is implemented.