ACCURACY AND RESPONSE TIME OF CONSUMER DIGITAL THERMOMETERS IN COOKED GROUND BEEF PATTIES AND CHICKEN BREASTS

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

Submitted to: American Meat Science Association Conference Reciprocal Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/24/2006
Publication Date: 6/16/2006
Citation: Liu, M., Vinyard, B.T., Callahan, J.A., Solomon, M.B. 2006. Accuracy and response time of consumer digital thermometers in cooked ground beef patties and chicken breasts [abstract]. American Meat Science Association 59th Reciprocal Meat Conference Proceedings. Paper No. 42P. June 18-21, 2006, Champaign, Illinois.

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. Ten units of three different commercially available consumer instant-read digital thermometers (D1, D2, D3) were tested for accuracy and response time compared to a calibrated thermocouple (TC) in preformed 80 percent (80B) and 90 percent (90B) lean ground beef patties cooked to 71C on gas grills (G) and electric griddles (F), and boneless (BC) and bone-in split (C) chicken breasts cooked to 77C on F and baked in consumer ovens (O) (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: 10 s (MT, manufacturer recommended time) and 30 s (ET, predetermined endpoint time) or recorded if the thermometer reached the target temperature before the MT or ET. The test was discontinued when the thermometer reached the target endpoint temperature or ET. At the MT, the percentage of beef and chicken samples registered as cooked was 0 - 28 percent for D1, 11 - 64 percent for D2, and 0 - 22 percent for D3. None of the 90B-G samples were registered as cooked using D1 or D3 and 80B-G, BC-O and C-O were not registered as cooked by D1. At either the MT or ET, the average temperature difference between the TC reading and the test thermometer reading were not different (p>0.05) within each thermometer among the meat products or cooking methods, except that the C-O difference was less (p<0.05) than the 90B-G for D2 at the MT. At the MT, the temperature difference range was 7C less to 14C higher than the TC for D1, 1 to 7C less than the TC for D2, and 6 to 9C less than the TC for D3. Increasing the time to the ET resulted in an increase in the percentage that the thermometer registered the beef and chicken samples as cooked; 19-64 percent for D1, 25-92 percent for D2, and 14-64 percent for D3. All test thermometers averaged temperatures less than the TC at the ET. The average temperature difference was 1 to 4C less for D1, 2 to 4C less for D2, and 2 to 4C less for D3. For those samples that reached the target endpoint temperature, the time for the thermometer to register the target temperature was 14 to 22 s for D1, 9 to 16 s for D2 and 16 to 21 s for D3. These results indicate that consumers using these digital 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 sensory quality of the products.