Accuracy, precision and response time of consumer fork, remote digital probe and disposable indicator thermometers for cooked ground beef patties and chicken breasts

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

Submitted to: Journal of Muscle Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2007
Publication Date: 4/2/2009
Citation: Liu, M., Vinyard, B.T., Callahan, J.A., Solomon, M.B. 2009. Accuracy, precision and response time of consumer fork, remote digital probe and disposable indicator thermometers for cooked ground beef patties and chicken breasts. Journal of Muscle Foods. 20(2):160-185.

Interpretive Summary: Consumers have been advised to use thermometers during cooking to ensure that ground beef and chicken products have been cooked to a safe internal temperature to prevent illness. A large study evaluating consumer instant-read thermometers (bimetals, digitals, forks, remotes, digital probe and disposable color change indicators) was conducted in meat products. In this paper, consumer instant-read fork, remote, digital probe and disposable color change indicator thermometers were tested in 80 percent and 90 percent lean ground beef patties cooked to 71° C on gas grills and electric griddles, and for boneless and bone-in split chicken breasts cooked to 77° C on gas grills and baked in consumer ovens. After the meat product reached the target endpoint temperature, the product was removed from the heating source and the thermometer was inserted into the cooked meat as close as possible to the thermocouple. Temperature readings were taken at the manufacturer recommended time and also at an extended time to determine the accuracy, response time and reliability of these consumer thermometers. All forks, remotes and the digital probe thermometers consistently measured temperatures less than the thermocouple at both the recommended and extended endpoint times. The color change indicating mechanism for disposable indicators was highly variable and often showed a partial color change at the recommended time and at the extended time. When using these thermometer models, most likely consumers would overcook their ground beef patties and chicken breasts which would prevent illness but would have a negative effect on the eating quality of the product.

Technical Abstract: Nine different commercially available instant-read consumer thermometers (forks, remotes, digital probe and disposable color change indicators) were tested for accuracy and precision compared to a calibrated thermocouple in 80 percent and 90 percent lean ground beef patties, and boneless and bone-in chicken breasts cooked on gas grills, electric griddles, and baked in consumer ovens. All models registered less than 42 percent of the products as cooked at the recommended insertion time except for one indicator model which registered greater than 50 percent of the products cooked in five meat product/cooking method combinations. Average thermometer readings deviated from the thermocouple by as much as 64 deg F. Increasing insertion time increased percentage of product registering as cooked and decreased the temperature difference. Measurement repeatability (precision) was high within and between individual thermometers of the same model. These results indicate that consumers using these thermometers would cook meat products to higher temperatures than necessary to destroy harmful microorganisms.