Can I trust my meat thermometer?

Ground red meat: 160°F, steaks and roasts: 145°F, all poultry: 165°F; how to know if that meat thermometer can be trusted.

After touting the use of a meat thermometer when cooking hamburger and even whole-muscle meats, pork chops, venison and more, how do you know if you can trust the reading it is giving you? Thermometer calibration is the key to this issue and can be solved without much difficulty. Thermometers are designed to calibrate within 2°F above or below the targeted temperature. There are two temperatures needed to calibrate a thermometer in its full range of use, one low temperature and one high temperature.

To calibrate a dial thermometer for use with cooked meat, high temperature calibration should be completed. First, bring distilled water to a rolling boil in a clean container. Second, place the thermometer into the water at least 2.5 inches deep but without touching the thermometer with the surface of the container and hold it for at least one minute. Third, compare the reading to the boiling temperature at your altitude. At sea level, 212°F is the temperature for pure boiling water. As a reference, the boiling temperature in relation to altitude is 211°F at 500 feet above sea level, 210°F at 1,000 feet above sea level, and 203°F at 5,000 feet above sea level. Adjust the thermometer using the hex bolt below the head of the thermometer until it reads 212°F or the proper temperature for boiling water at the given altitude. It is important to use distilled water because dissolved solutes found in tap water can alter freezing and melting points quite significantly. If the thermometer is not adjustable and is more than 2°F off in either direction, discontinue using the thermometer until it is serviced. If it cannot be serviced, replace the thermometer.

To calibrate a thermometer for use at refrigerated temperatures, low temperature calibration should be completed. First, add crushed ice to distilled water in a clean container. Second, place the thermometer into the water at least 2.5 inches deep but without touching the thermometer with the surface of the container and hold it for at least one minute in the ice water slush. Third, compare the reading to the temperature the ice water slush should be, 32°F. If the temperature is more than 2°F above or below 32°F,adjust the thermometer using the hex bolt below the head of the thermometer until it reads 32°F.

If thermometer calibration is needed for use with a HACCP plan, it is necessary to calibrate daily or weekly, depending on the size of the operation. Additionally, a National Institute of Standards and Technology (NIST) certified reference thermometer is needed to compare thermometer readings of certain types of thermometers where the boiling water or ice bath methods will not work. Reference thermometers that are NIST certified are available through a range of commercial vendors.

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