Accuracy of consumer fork, remote, and digital probe thermometers in cooked ground beef patties and chicken breasts

Authors: Liu, Martha; Vinyard, Bryan; BOARMAN, JANICE; Solomon, Morse

Submitted to: USDA Annual Food Safety Research Planning Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2007
Publication Date: 2/21/2007
Citation: Liu, M., Vinyard, B.T., Callahan, J.A., Solomon, M.B. 2007. Accuracy of consumer fork, remote, and digital probe thermometers in cooked ground beef patties and chicken breasts [abstract]. USDA Annual Food Safety Research Planning Meeting.

Interpretive Summary:

Technical Abstract: Use of a thermometer is the only way to determine if meat products have been cooked to an internal temperature necessary to inactivate pathogens. To date, the accuracy and reliability of consumer instant-read thermometers have only been evaluated in water-baths, not in meat products. For each of the seven models of thermometers examined in this study, three forks (F1, F2, F3), three remotes (R1, R2, R3), and one digital probe (DP), 10 individual thermometers were used. These thermometers were tested for accuracy compared to a calibrated thermocouple (TC) in preformed 80 percent and 90 percent lean ground beef patties cooked to 160 deg F on gas grills and electric griddles, and boneless and bone-in chicken breasts cooked to 170 deg F on gas grills and baked in consumer ovens (n=36 for each meat product and cooking method). Once products reached the target endpoint temperature using the TC, the product was removed from the heat source and the test thermometer was inserted into the product parallel and as close as possible to the TC. Times and temperatures of the test thermometer and TC were recorded at two predetermined times: manufacturer or FSIS recommended time (RT; 15 s for forks and DP and 10 s for remotes) and at a predetermined endpoint time (EP; 30 s) or recorded if the thermometer reached the target temperature before the RT or EP. The test was discontinued when the thermometer reached the target endpoint temperature or EP. At the RT, the percentage of beef and chicken samples registered as cooked was 0-11 percent for F1, 0-42 percent for F2, 0-8 percent for F3, 0-3 percent for R1, 0-3 percent for R2, 0 percent for R3, and 0-28 percent for the DP. All test thermometers averaged temperatures less than the TC at the RT; the temperature range was 14 to 19 deg F less than the TC for F1, 6 to 14 deg F less for F2, 14 to 20 deg F less for F3, 25 to 36 deg F for R1, 28 to 40 deg F less for R2, 41 to 64 deg F less for R3, and 8.2 to 26.0 deg F less than the TC for DP. At the EP, the percentage of beef and chicken samples registered as cooked was 3-33 percent for F1, 0-72 percent for F2, 3-42 percent for F3, 3-56 percent for R1, 36-75 percent for R2, 0-44 percent for R3, and 0-44 percent for the DP. These results indicate that consumers using these fork, remote, and digital probe thermometers would cook ground beef patties and chicken breasts to higher temperatures than necessary to destroy harmful microorganisms. Although cooking to these temperatures would ensure a microbiologically safe product, it would negatively affect the quality of the products.