Cooking time and temperature vital in controlling pathogens

Findings were based on US Department of Agriculture-Food Safety and Inspection Service (USDA-FSIS) thermal processing guidance.

Results confirmed that cooking temperatures and times used in the meat and poultry industry following USDA-FSIS guidance for thermal lethality are sufficient to kill Listeria monocytogenes, Salmonella, and shiga-toxin producing E. coli (STEC) in roast beef, turkey deli-breast, and boneless hams when  temperature met or exceeded 62.8°C.

The pathogen reduction levels all met or exceeded regulatory requirements or recommendations for the products tested.

However, when cooking roast beef to 54.4°C, USDA-FSIS thermal processing guidance for Salmonella was not supported—suggesting that additional cooking time or higher temperatures are needed to achieve a target pathogen reduction.

In all product types inactivation rates for STEC were similar to Salmonella at 140, 150 and 160°F and were comparable to or less than times reported in USDA-FSIS Appendix A.

Time-temperature controls​

The aim of the research was to create data to develop scientifically-validated, time-temperature tables as tools for assuring regulatory compliance and pathogen destruction.

It also provides the basis for time-temperature tables in product categories that will cover ready-to-eat (RTE) meat products and thermal processes in the US meat industry.

Thermal treatments are critical for controlling foodborne pathogens in RTE meat and poultry products, said Sindelara et al.

Microbial resistance to thermal processes can be affected by the level and length of heat exposure and various intrinsic factors such as fat, salt or water concentration.

The wide application of limited research may be of concern since the heat resistance of microorganisms can be affected by the targeted pathogen, cell concentration, phase of growth, amount of strain, and exposure to stressors such as acid or salt, said the researchers.

Tolerance to heat​

L. monocytogenes showed greater thermotolerance than Salmonella and STEC under all conditions.

“For example, >5-log reduction ofSalmonellaand STEC in turkey was achieved instantaneously at 71.1°C, whereas L. monocytogenes required a 10 second holdtime. At 60°C (140°F), >5-log reduction of L. monocytogenes required 30 and 50 minutes in turkey and ham, respectively, as compared to <12 minutes for Salmonella and STEC​,” said the researchers.

At the lowest temperature tested (54.4°C/130°F), >5-log reduction of Salmonella, STEC and L. monocytogenes in all product types was achieved in <2, 2.8 and 4.6 hours, respectively.

The scientific approach were to measure D- and z-values for Salmonella, L. monocytogenes, and STEC in roast beef, turkey deli-breast, and boneless ham following cooking temperatures and times commonly used in the meat industry.

Generated D- and z- values could then be utilized in pathogen modeling programs or to generate simple thermal processing tools such as time/temperature thermal processing tables valid for specific product/pathogen combinations.

Ground turkey breast, ground roast beef and ground ham were inoculated with 8 log CFU/g L. monocytogenes or Salmonella (5-strain mix) or STEC (7-strain mix).

The researchers added that other variables that warrant further research and can impact thermal lethality are intrinsic factors (fat, water activity, pH, etc), physical differences (diameter, size, shape, etc), or extrinsic factors (type of heat source, presence/level of humidity, speed of cooking.

Source: AMIF Final Report; July 2013

“Developing Validated Time-Temperature Thermal Processing Guidelines for Ready-To-Eat Deli Meat and Poultry Products”​

Authors: Jeffrey J. Sindelara, Kathleen Glass, Robert Hanson